In 2001, 19-year-old Prithviraj underwent a screen-test by Director Fazil for one of his projects at that time. Even though that project never materialised, Fazil recommended him to Director Ranjith, who was planning his second directorial venture, Nandanam. Ranjith instructed Prithviraj to grow a beard to look mature. Nandanam released in 2002. Though Nandanam is his debut film, it released after Nakshathrakkannulla Rajakumaran Avanundoru Rajakumari. After Nandanam, Prithviraj appeared in films directed by Lohithadas, Vinayan, Kamal and Bhadran. Shyamaprasad, who cast him in lead role in his film Akale, said that Prithviraj's advantages are his talent and intelligence irrespective of his box office successes.

The son of actors Sukumaran and Mallika, Prithviraj was first spotted by Director Fazil. Fazil's screen test of Prithviraj prompted Director Ranjith to cast him in the 2002 romantic-drama film Nandanam, his acting debut. Prithviraj has won two Kerala State Film Awards for Best Actor for his performances in Vaasthavam (2006) and Ayalum Njanum Thammil & Celluloid (both 2012), one Tamil Nadu State Award for Best Villain for his performance in Kaaviya Thalaivan (2014), and a National Film Award (as producer) for Indian Rupee (2011). He has co-produced films under the production house August Cinema since 2010, and ended his partnership there in 2017. He later launched his independent production house, Prithviraj Productions on March 2018. Later through social media he confirmed that he would be joining hands with popular brand Sony Pictures, for his maiden home production and the movie has been named as Nine.

In 2005, Prithviraj Sukumaran debuted in Tamil through Kana Kandaen. In 2006, Prithviraj co-starred with actor Bhagyaraj's daughter Saranya Bhagyaraj in Parijatham. It has been acclaimed as a hit and gave the actor a turning point in his Tamil film career. In 2007, Prithviraj co-starred in Mozhi. He also starred in Satham Podathey and Kannamoochi Yenada in the same year. In 2008, Prithviraj starred in Vellithirai, the Tamil remake of Udayananu Tharam. Rediff described his performance: "Prithviraj ... makes the best of his assets -- his expressive eyes, which glint in fury, soften with love, or brim over with frustrated tears." The Tamil remake of Classmates, titled Ninaithale Inikkum, was released in 2009. He played a cop in Mani Ratnam's Raavanan in 2010 with Vikram playing the main protagonist and his performance was critically acclaimed. Prithviraj played one of the main characters in Director Vasanthabalan's big budget period film Kaaviya Thalaivan, in which he co-stars with Siddharth.

In 2006, he played the role of Sub Inspector Solomon Joseph in Vargam. After Vargam, Prithviraj acted in Vaasthavam with the same Director, M. Padmakumar, for which he received the Kerala State Film Award for Best Actor and became the youngest actor to win the award. The same year he starred in Lal Jose's Classmates. In 2007, he starred in Chocolate, directed by Shafi. In 2008, he starred in Thalappavu, (directed by Madhupal) and Thirakkatha, (directed by Ranjith), in which he took up roles which serve as pivotal characters. One of the reviews of Thalappavu describes it as a film which is truly the coming-of-age film for Prithviraj, the actor and that there is a spartan dignity that he brings to his commanding portrayal of the Naxalite Joseph. The Sify review of Thirakkatha describes it as a "genuine attempt that keeps the viewer engaged until the end". Both Thalappavu and Thirakkatha shared the award for the best film in the Film Critics Award for 2008. He also made a special appearance in Anjali Menon's Manjadikuru.

Prithviraj debuted as a singer in Puthiya Mukham (2009) by singing the title song of the film; "Kaane Kaane".

Prithviraj Sukumaran debuted in Telugu through Police Police, which was released in 2010. Besides, Prithviraj has had many of his Malayalam films dubbed into Telugu such as Sivapuram in 2006, which was the dubbing of Ananthabhadram and ATM in 2010, which was the dubbing of Robin Hood. The dubbed version of Urumi released in August 2011.

Prithviraj married BBC India reporter Supriya Menon on 25 April 2011, in a private ceremony held at Palakkad. They have a daughter named Alankrita Menon Prithviraj, born in 2014. Prithviraj's family resides at Kochi , Kerala.

In 2012, Prithviraj Sukumaran started a production company named August Cinema with Cinematographer turned Director Santosh Sivan and businessman Shaji Nadesan. In 2015, actor Arya joined the production company. However, in 2017, he announced on his Facebook page that he is quitting the company. In March 2018, Prithviraj announced the launch of his independent production company named Prithviraj Productions.Later the actor announced that his production company was getting into a collaboration with Sony Pictures India for its maiden venture.

In 2014, Prithviraj's first major release was London Bridge, which failed at box office; followed by 7th Day, which turned out to become a commercial success. He also did a cameo role in the Mammootty led Munnariyippu. His third release of the year, SapthamashreeThaskaraha was praised by critics and audiences alike. His first release of 2015 was Picket 43. His second movie of 2015 was Shyamaprasad's Ivide. Even though the movie did not match up to its expectations, Prithviraj was hugely praised for his outstanding acting in the movie. Varun Blake (Prithviraj's character in Ivide) is considered to be one of his best performances till date. He next appeared in Lijo Jose Pellissery's Double Barrel, which was appreciated for its novelty. His most successful film of the year was Ennu Ninte Moideen, which narrated the tragic love tale of Kanchanamala and Moideen that happened in the 1960s in Mukkam, a riverside village in Kerala. The film opened to critical acclaim, with several critics regarding it as one of the greatest romance films made in Malayalam. His role as Moideen in the film is regarded as one of the best in his career. His next releases Amar Akbar Anthony and Anarkali became back to back big hits, thus completing a hat-trick of hits ending the year.

Prithviraj had four releases in 2016, debuting with Paavada, a family drama in which he played a drunkard. It met with positive response and was a commercial success, grossing ₹16.34 crore from Kerala box office and ran for 100 days in theatres. His following releases Darvinte Parinamam and James & Alice met with mixed reviews, the former told the story of an ordinary man dealing with a local goon and the latter was a family drama that discussed the matter of life and death. His last release, Oozham, an action thriller directed by Jeethu Joseph was a commercial success, earning ₹15.25 crore in 25 days. He played a demolition expert. In 2017, he starred in the horror film Ezra, which became one of the highest-grossing Malayalam films of the year, grossing ₹50 crore worldwide, with ₹33 crore from Kerala box office.