When picking a name for her adult career, she has said that Sunny is her real name and Leone was picked by Bob Guccione, former owner of Penthouse magazine. She posed for Penthouse magazine, and was named Penthouse Pet of the Month for the March 2001 issue, followed by a feature in the Holiday 2001 edition of Hustler magazine as a Hustler Honey. She has also appeared in other magazines including Cheri, Mystique Magazine, High Society, Swank, AVN Online, Leg World, Club International and Lowrider, while her online credits include ModFX Models, Suze Randall, Ken Marcus and Mac & Bumble.

Leone has made appearances at events such as the 2002 SEMA International Auto Salon, the 2002 Extreme Autofest Pomona and the 2006 World Series of Poker in Las Vegas. Sunny has also been the hostess at events in clubs like the Mansion in Miami and the Highlands in Hollywood.

In 2003, she was named "Penthouse Pet of the Year" and starred in the video Penthouse Pets in Paradise alongside Tera Patrick and Kyla Cole. In 2005 Adam & Eve appointed her as their West Coast Internet Sales Representative.

In 2004, she was part of No More Bush Girls, in which she and several other popular adult actresses shaved off their pubic hair in protest of the George W. Bush presidency. In May 2008, she shot a promotional video for Declare Yourself, a nonprofit, nonpartisan voter registration campaign targeting 18- to 29-year-olds. She indicated that Barack Obama would be her choice in the 2008 U.S. presidential election, primarily because she felt he was more Business friendly to the adult industry than his opponent John McCain. She also released a public Service announcement on behalf of the ASACP, reminding adult webmasters to protect their sites from children by having an RTA label on it.

In 2005, she was mentioned in Forbes magazine for a story on Vivid Entertainment. Leone has also been featured in mainstream publications like FHM, Front and Jane magazine. In 2007, along with the other Vivid Girls, she was seen in a 48' high holiday Billboard in Times Square at W. 48th Street and Seventh Avenue. Leone is also one of the Penthouse Pets who appears in the PlayStation Portable game Pocket Pool. She was also featured in a coffee table book titled Naked Ambition: An R Rated Look at an X Rated Industry by Michael Grecco.

In addition to her film career, Leone has been part of the Vivid Comedy Tour, and has modelled for the Vivid Footwear collection. Leone has also participated in events like the Vivid/ClubJenna Lingerie Bowl and Vivid's Hot Rod Night. Doc Johnson launched a pocket pal in 2006 moulded to her vagina, and in 2008 released the Sunny Leone Exciter vibrator. Control MFG currently uses Leone's image along with other Vivid girls to market their line of skateboards. She is paired with Gab Ekoe, one of the Team Control riders. She also indicated that she plans to launch her own line of lingerie and other Sunny-branded products including a Diamond jewellery line.

Leone was voted number 13 (up from number 41 in 2007) on Genesis magazine's "Top 100 Porn stars" list, number 34 on Desiclubs.com's Top 50 Coolest Desis of 2004, and one of the "40 under 40" ranking on AVN Online magazine. In 2010, she was named by Maxim as one of the 12 top female stars in porn. She was voted number 82 in the Top 99 Women for 2012 in AskMen.com's list.

A 2008 Eye Weekly article reported that "Leone does her best to maintain a link to Sikh traditions, even if more in theory than in practice. But she's unlikely to disavow her career path due to religion" and that Leone said "Girls will leave the industry claiming that they found God. Well, the fact is, God has always been with them the entire time." In a 2010 interview, she said

In September 2009, an iPhone application consisting of a collection of non-nude photos, some videos and a porn star-penned blog was approved by Apple for sale in the iTunes store, making it the first officially sanctioned application featuring a porn star. By February 2010, the app had been removed by Apple from the store.

In 2011, she participated in the Indian reality series Bigg Boss, entering the house on day 49. However she refused to divulge her porn star status, and replied to fellow house-mate Pooja Bedi that she was a model and a TV star in America for the last ten years or so. It was reported that she caused a stir in the larger populace with her Twitter feed gaining 8,000 new followers in just 2 days and Google saying searches for her experienced a "breakout". There were also complaints lodged with the Indian Ministry of Information and Broadcasting alleging that the Colors TV channel was promoting pornography by having Leone appear on the show; among those who filed are the Indian Artistes and Actors Forum and Anurag Thakur, member of Lok Sabha and head of the Bharatiya Janata Party's youth wing.

In June 2006, Leone became an American citizen, but stated she planned to remain a dual citizen of Canada. On 14 April 2012, Leone announced that she was now a resident of India explaining in an interview to The New Indian Express that she was an Overseas Citizen of India and that she was eligible for overseas citizenship because her parents lived in India. She applied for it prior to filming Jism 2.

During her stay in the Bigg Boss house, Sunny was approached by Bollywood film-maker Mahesh Bhatt who entered the house briefly to offer her the lead role in Jism 2 (the sequel to the 2003 film Jism). She accepted it, which resulted in Pooja Bhatt's production house, Fish Eye Network and Leone's agent discussing the movie further. Leone's entered Bollywood in 2012 with the film Jism 2 to weak critical reception but was commercially successful. Sunny Leone signed her second Bollywood film, "Ragini MMS 2". Ragini MMS, sequel to Ekta Kapoor's crossover horror movie Ragini MMS. Sunny Leone featured in an item number in the Sanjay Gupta and Ekta Kapoor's 2013 film Shootout at Wadala. She further started filming for Kaizad Gustad's Jackpot in which she plays a femme fatale. Jackpot released on 13 December 2013 and was panned by critics.

Her first release of 2014 was the much anticipated horror film Ragini MMS 2, which proved to be a box-office hit. Leone's performance received all round praise with critic Mohar Basu calling her work a "revelation". Critic Taran Adarsh also noted that Leone," carries off her character with supreme confidence" In November 2013, she had confirmed that she would make her Tamil film debut in Vadacurry which released in May 2014 and featured her in a special appearance. She next appeared in the item number Pink Lips for the film Hate Story 2, . After giving a hit number Pink Lips, she appeared once again in Shake That Booty opposite Mika Singh from his film Balwinder Singh Famous Ho Gaya. She made her acting debut in the Telugu film industry by appearing in a cameo in Current Theega opposite Manchu Manoj and Rakul Preet Singh where she played a school Teacher.

A police first information report was filed against her in May 2015 after a woman at Mumbai, India, complained that Leone's website, Sunny Leone.com, was destroying the Indian culture. Thane police's cyber cell at Ramnagar booked her for sections 292, 292A, 294 which could land her into jail, fine or both. Senior police inspector JK Sawant stated, "We cannot block the website, but will ask the operator to remove objectionable content."

In April 2016 Leone published an e-book of love stories entitled Sweet Dreams. The work was well received by the Hindustan Times, which commented, "Sunny’s stories are relentlessly optimistic. The characters are not complicated or unpleasant and exist in a world that veers on the border of Valentine’s Land with its floating pink hearts and soft focus lighting."

In 2017 new year, a pro-Kannada group Rakshana Vedike Yuva Sene protested against the event ‘Sunny Night in Bengaluru NYE 2018’ in Bengaluru. Sunny Leone was to perform at this event and the group argued that due to her pornographic past, she shouldn’t be allowed in the event. The protesters even threatened mass suicide and fearing that there can be a law and order situation, Karnataka home minister Ramalinga Reddy denied permission to this event.

In 2018 a social Activist has lodged a complaint against Sunny Leone at the Nazarethpet police station in Chennai. He stated that the Actress is promoting pornography which is against the Indian nation’s law. He also added that this will majorly dent the Indian culture and spoil the moral fabric of the society.