In 1991, Devgn began his professional career in Phool Aur Kaante and received a Filmfare Award for Best Male Debut. He costarred with Madhoo. In his opening scene, Devgn performed a split while balancing between two motorcycles. His next film was Jigar (1992), a Bollywood martial arts film co-starring Karisma Kapoor. It was released on Diwali weekend and became the seventh-highest-grossing movie of that year, taking ₹7 crore (US$1.1 million) at the box office. https://shoutmemovies.blogspot.in/ In 1993, Devgn starred in Dil Hai Betaab, a movie about a love triangle and romantic themes such as revenge. He next featured in Divya Shakti and then Sangram, a story of enmity between two fathers. Devgan then worked with Deepak Bahry, who directed the action film Ek Hi Raasta, and with Deepak Pawar, who directed Platform. Other releases that year were Shaktiman, Dhanwan and Bedardi.

In 1994, Devgn starred in Harry Baweja's romantic action movie Dilwale. He played the part of Arun Saxena, a man with intellectual impairment. The movie was the tenth-highest-grossing movie of the year. His next release was Kanoon and then Kuku Kohli's Suhaag with Akshay Kumar. The movie was about two friends. Devgn played Ajay Sharma/Malhotra. Suhaag was the seventh-highest-grossing movie of the year. His next film was Vijaypath. Shooting dates for Vijaypath clashed with those of Karan Arjun which Devgn declined. Vijaypath was the eighth-highest-grossing film of the year.

In 1995, Devgn appeared in Mahesh Bhatt's movie Naajayaz and then Hulchul directed by Milan Luthria. Kajol co-starred. Devgn and Kajol then appeared in Gundaraj which did not perform well at the box office. His next release was Haqeeqat costarring with Tabu. This film was the eleventh-highest-grossing movie of the year.

In 1996, Devgn starred in the action movie Jung with Mithun Chakraborty, Rambha and Aditya Pancholi. His next release was an action movie called Jaan, with Twinkle Khanna. He then starred in Harry Baweja's film Diljale, where he played a terrorist character called Shaka.

In 1997, Devgn starred in a poorly received movie, Itihaas, with Twinkle Khanna. His next release was Indra Kumar's romantic comedy Ishq with Aamir Khan, Juhi Chawla and Kajol. In this successful film, Devgn played Ajay, a rich boy in love with a poor girl, (Kajol). The film grossed ₹30 crore (US$4.6 million). The film was the fourth-highest-grossing film of the year.

In 1998, Devgn gave a critically acclaimed performance in Mahesh Bhatt's drama, Zakhm, and received his first National Film Award for Best Actor. In 1999, in Hum Dil De Chuke Sanam, Devgn played Vanraj, a man who tries to unite his wife with her lover. Devgn then starred in Major Saab with Amitabh Bachchan and Sonali Bendre where he played the character of an army officer. The movie was successful and was the tenth-highest-grossing film of the year. He next starred with Kajol in Anees Bazmee's second film, the romantic comedy Pyaar To Hona Hi Tha, a remake of the Hollywood hit French Kiss. It grossed 302,500,000 Indian rupees. Devgn's next release was Mahesh Bhatt's Zakhm. The plot examines communal tension in Mumbai during riots. Devgn played a man who is fed up with religious conflict. Devgn won several awards for his performance, including the National Film Award for Best Actor and the Star Screen Award for Best Actor.

In 1999, Devgn starred in the romantic drama Hum Dil De Chuke Sanam, in which he played Vanraj, a man who tries to help his wife (Aishwarya Rai) reunite with her lover (Salman Khan). Hum Dil De Chuke Sanam marked a significant turning point in Devgan's career. The film, an adaptation of Maitreyi Devi's Bengali novel Na Hanyate, was directed by Sanjay Leela Bhansali and co-starred Salman Khan and Aishwarya Rai. Devgn was highly praised for his performance. Rediff said: "Ajay's role reminds you of one he did in another film, Pyar Tho Hona Hi Tha. There he is searching for the boyfriend of the girl he secretly loves. But intense scenes are his forte and he does well here. He's particularly good in the scene where he gets exasperated with his wife's stubbornness and strives to keep his cool." The movie was successful and Devgan was nominated for the Filmfare best actor award. After that, he appeared in Hindustan Ki Kasam with Amitabh Bachchan and Sonali Bendre. He then worked with the Director Milan Luthria in Kachche Dhaage, with Saif Ali Khan and Manisha Koirala. The movie was a box-office hit. He then performed in the successful movie Hogi Pyaar Ki Jeet, a romantic comedy, and then in his home production movie with Kajol, and Director, Prakash Jha. The film was titled Dil Kya Kare. His other movies in 1999 were Gair and Thakshak in which he played a strong, silent man.

Devgn's production company Ajay Devgn Films, was established in 2000. The company's first film was Raju Chacha, (2000) starring Devgan and Kajol. In 2008, Devgn made his directorial debut and co-produced U Me Aur Hum. Devgn was part of the drama film's team of four Writers. The film tells the story of a woman (Kajol) who has a very weak memory and even forgets her own husband. Taran Adarsh, a film critic, described it as "a well-made, absorbing love story that's high on the emotional quotient."

In 2001, Devgn starred in another moderately successful film; Yeh Raaste Hain Pyaar Ke with Madhuri Dixit and Preity Zinta. His next release was Lajja, with Manisha Koirala, Madhuri Dixit, Jackie Shroff and Anil Kapoor. He was nominated for the Filmfare Best Supporting Actor Award. However, the film was not popular with the public. Mahesh Manjrekar's Tera Mera Saath Rahen followed.

In 2002, Devgn performed in Ram Gopal Varma's fictional examination of the Mumbai underworld in the film Company. Devgn played a gangster named Malik. Both Company and Devgn's performance received critical acclaim. As Taran Adarsh reviewed: "Ajay Devgn enacts his role to perfection. A controlled performance, the actor takes to this complex character like a fish takes to water. He underplays his part with admirable ease." Devgan was nominated for the Filmfare Best Actor Award and won the Filmfare Critics Award for Best Actor. Devgn's next release was David Dhawan's comedy Hum Kisise Kum Nahin, with Amitabh Bachchan, Sanjay Dutt and Aishwarya Rai. The same year, he played the role of Bhagat Singh, in Rajkumar Santoshi's biopic The Legend of Bhagat Singh. His performance was well received by critics. Taran Adarsh said, "Ajay Devgn has lived the role. To state that he is excellent would be an understatement. His performance is bound to win admiration from cinegoers, besides fetching awards." The film was released on 7 June 2002 and went on to win two National Film Awards, including the National Film Award for Best Feature Film in Hindi, and three Filmfare Awards, including the Filmfare Critics Award for Best Movie. Despite these awards, and Devgn winning his second National Film Award for Best Actor for his performance, the film was not popular with the public. Devgn went on to perform in Anees Bazmee's Deewangee. The film was partially inspired by william Diehl's novel, Primal Fear. The film earned Devgn several awards for his role including a Filmfare Best Villain Award, the Star Screen Award for Best Villain and the Zee Cine Award for Best Actor in a Negative Role. The film was a success at the box office.

In 2003, Devgn starred in Ram Gopal Verma's horror film Bhoot, opposite Urmila Matondkar. The film was appreciated critically and performed well at the box office. He then starred in the action thriller Qayamat: City Under Threat with the Actress debutante, Neha Dhupia. The film was a commercial success. Devgn next performed in Milan Luthria's romantic film Chori Chori, opposite Rani Mukherji and Sonali Bendre. This film did not succeed at the box office. Devgn's next release of the year was Prakash Jha's Gangaajal. The film was set in the time of the blinding incident in Bhagalpur, Bihar. Rediff.com said, "Ajay Devgan pulls up an ace with a part tailormade to reinforce his seething-under-the-surface angry hero image. To his credit (and the director's), he brings style and grace to a largely stereotypical, righteous protagonist. To a great extent, his presence covers up the film's patchiness in the second half." Devgn was nominated for the Filmfare Best Actor Award for this performance. He then worked in Rohit Shetty's directional debut Zameen and J. P. Dutta's war film LOC Kargil.

In 2004, Devgn was cast with Amitabh Bachchan, Aishwarya Rai and Akshay Kumar in Rajkumar Santoshi's action thriller Khakee. The film was released on 23 January 2004. It received positive reviews and became one of the highest-grossing films of 2004. In Khakee, Devgn once again played a villain. His performance as a police officer turned murderer was well received by critics. Taran Adarsh said: "Ajay Devgan adds yet another feather in his cap with a performance that could've been played only by a master performer. His confrontations with Amitabh Bachchan are exemplary." Later in 2004, Devgn appeared in Indra Kumar's Masti: Sanam Teri Kasam. He also starred in Yuva.

2005 was a less successful year for Devgn. His movies were not financially successful. They included Insan, Blackmail, Main Aisa Hi Hoon, Tango Charlie and Shikhar. However, the films Kaal and Apaharan did well. For his performance in Apaharan, Devgn was nominated for the National Film Award for Best Actor and the Filmfare Best Actor Award. His performance as a villain in Kaal also earned him a nomination for the Filmfare Best Villain Award.

In 2006, Devgn also starred in Rohit Shetty's Golmaal. It had two sequels Golmaal Returns and Golmaal 3. In the same year, Devgn was featured in a short documentary about the Mumbai floods of 2005 titled The Awakening.

In 2007 Devgn starred in two movies, Director Anubhav Sinha's action thriller Cash and Ram Gopal Varma Ki Aag.

Again in 2008, Devgn performed in Rohit Shetty's comedy Golmaal Returns, a sequel to the 2006 film Golmaal: Fun Unlimited about a mistrustful wife who believed her husband was unfaithful. The Indian Express said the screenplay was derivative, concluding: "There is nothing particularly new about a suspicious wife keeping tabs on her husband, and there is nothing particularly new in the way Ajay-Kareena play it." Golmaal Returns was a financial success with global revenues of ₹79.25 crore (US$12 million).

In 2009, Devgn released his home production All the Best: Fun Begins, which was directed by Rohit Shetty and starred Devgn, Sanjay Dutt, Fardeen Khan, Bipasha Basu and Mugdha Godse. The film was released on 16 October 2009, and was the ninth-highest-grossing Bollywood film of 2009.

Devgn then starred in Priyadarshan's action-thriller film Aakrosh. The movie explores the subject of honour killings. Aakrosh received some positive reviews, but was financially unsuccessful. At the end of 2010, Devgn worked again with Rohit Shetty in Golmaal 3, a sequel to Golmaal Returns (2008). Although, like its predecessor, the film received mixed reviews, it was the most successful of the Golmaal series, earning more than ₹107 crore (US$16 million). Devgn also worked as a voice Artist in Toonpur Ka Super Hero, an animated film.

In 2011, Devgn performed with Emraan Hashmi in Madhur Bhandarkar's comedy Dil Toh Baccha Hai Ji. He was a narrator in Yamla Pagla Deewana and also made a cameo appearance in Ready. Devgn starred in Rohit Shetty's Singham. Taran Adarsh said: "The title means 'Lion' and Ajay is in the centre of the battle between good and evil. Ajay is well known for the lines, "aataa maajhi satakli". The embodiment of screen masculinity, Ajay enacts the central character of a righteous, hardhearted cop with flourish. He brings alive on screen a larger-than-life hero character with determined conviction, which renders you thunderstruck. One of the few actors who underplays his part admirably, he returns to the over-the-top-action genre of films with this one. In a nutshell, his performance plays a pivotal role in carrying the film to the winning post." He then starred David Dhawan's action comedy film Rascals.

Devgn also starred in Ashwni Dhir's romantic action comedy film Son of Sardaar, which was a joint production with Viacom 18 Motion Pictures. The film was released on 13 November 2012. Despite competition with Yash Raj's film Jab Tak Hai Jaan, Son of Sardaar was a financial success. It made ₹150 crore (US$23 million).

In 2013, Devgn featured in the critically and commercially unsuccessful remake of Himmatwala. Devgn next featured in Prakash Jha's political drama Satyagraha.

In 2014, Devgn featured in Rohit Shetty's Singham Returns, a sequel to Singham.Singham Returns received mixed reviews from Indian critics. Taran Adarsh of Bollywood Hungama gave it 4 stars and said: "The film is a complete mass entertainer with power-packed drama, hi-intensity dialogue and towering performances as its aces. The brand value attached to it coupled with a long weekend will help the film reap a harvest and rule the box office in days to come.". Collection of over ₹32.09 crore (US$4.9 million) on the first day of its release in India. Domestic net of Singham Returns are ₹140.62 crore (US$22 million). Devgn next featured in Prabhu Deva's Action Jackson which did not perform well at box office.

In 2015, Devgn starred in Drishyam, directed by Nishikant Kamat. The film received positive reviews, Meena Iyer of The Times of India gave the film four out of five stars, describing it as "A suspense drama with a nail-biting finish." She praised Devgan's performances: "Ajay, who is the prey here, shines in his role of the protective father.". The film was successful at the box office, by the end of its sixth week, the film had grossed about ₹76.48 crore (US$12 million) at the domestic box office.

In 2016, Devgn was seen in his own production, Shivaay, which released around Diwali 2016. Shivaay is an action drama movie. Shivaay opened to mixed reviews and grossed more than ₹146 crore (US$22 million)

In 2017, Devgn featured in Director Milan Luthria's Baadshaho and Rohit Shetty's Golmaal Again. Both films were commercial successes.In the dry spell of Bollywood where big names like Shahrukh Khan and Salman Khan were unable to give a single hit Devgn gave two back to back hits in 2 months. While Baadshaho was a hit, Golmaal Again became the highest-grossing film of 2017 collecting 100 crores in 4 days of its release and a lifetime collection of 205 crores at the Indian box office while making a hefty 300 crores at worldwide box office

In 2018, Ajay Devgn released his first Marathi production Aapla Manus. The movie was in Marathi language. It was directed by Satish Rajwade and starred Nana Patekar, Iravati Harshe, and Sumeet Raghavan. The film was produced by Ajay Devgn, Nana Patekar, Abhinav Shuklaa, Manish Mishra, & Rohit Choudhary and released on 9 February 2018. The story was a dramatic thriller and written by Vivek Bele. The film was distributed by Viacom 18 Motion Pictures. .