During her career in the porn industry, which she began in 2001, she appeared in over 400 releases. In 2004, she was voted "the French's favorite porn actress" in a readers' poll organized by trade journal Hot Vidéo. She also appeared in several Italian and Spanish productions, working for Directors such as Mario Salieri. She performed alongside Rocco Siffredi in Who fucked Rocco ?, Fashionistas Safado: The Challenge and Fashionistas Safado: Berlin, the latter two being directed by John Stagliano.

She shot her first American films in 2003. In 2005, she decided to focus on her work in the United States whose industry offered better opportunities. During the next few years, she divided her time between France and the US, working mostly in the latter country. In December 2006, she became the first French Actress to sign an exclusive performing contract with Digital Playground.

In May 2006, she got breast implants. Her first film with her new breasts, French ConneXion of Marc Dorcel Productions, came out at the beginning of 2007. In the meantime, Tran also modelled for the cover of Marquis magazine, a leader in fetishism. She also continued working and touring as an exotic Dancer in nightclubs of various countries.

She originally performed using the stage name Katsumi (a Common given name in Japan for both sexes), but she was barred by a French judge in Créteil in January 2007 from using the name, after a woman named Mary Katsumi sued over the resemblance to her own name. Although she had informed the websites that she had changed her stage name, many outlets kept referring to her as "Katsumi". She was eventually sued again a few months later and, in September 2007, was fined €20,000, having been deemed responsible for various violations of the ban.

In July 2008, Céline Tran released My Fucking Life, a French-language film made for Marc Dorcel Studios. The movie is partly a documentary on Tran's daily life over a year, with a look at her shoots in Las Vegas, on set during filming in Porn Valley, along with a bit of her personal life. In 2008, she was part of the cast of Pirates II: Stagnetti's Revenge, one of the most expensive porn films ever produced. In 2012, she directed another feature for Dorcel, In bed with Katsuni. In 2011, Complex ranked Tran fourteenth on their list of "The Top 100 Hottest Porn Stars Right Now" and third on their list of "The Top 50 Hottest Asian Porn Stars of All Time".

During her adult career, Tran's personality and success in the United States attracted the attention of the French mainstream medias. In October 2009 she was a guest in the popular talk show On n'est pas couché. In the early 2010s, she wrote articles about the porn industry for the magazines Les Inrockuptibles and Le Nouvel Observateur.

In 2010-2011, she hosted on the French channel MCM Katsuni's sexy mangas, a TV show dedicated to hentai. The show was eventually canceled in March 2011 due to a decision of France's Superior Council of Audiovisual content. Among other appearances in the French mainstream media, she played herself in the successful comedy film Porn in the Hood (2012). In 2013, she was one the porn stars interviewed in the American documentary film Aroused, directed by Photographer Deborah Anderson.

On 14 August 2013 Tran announced that she was retiring from porn in order to focus on "a new kind of entertainment". She relocated to France and has been using since then her birth name, Céline Tran. A few months after her retirement, she was inducted into the AVN Hall of Fame.

Tran has since appeared in several mainstream productions. In 2014, she played a recurring character in the French web fiction Le Visiteur du futur. Also in 2014, she wrote the script for Heart Breaker, the sixth volume of the French comic book horror series DoggyBags. In 2016, she started working as a DJ and writing a blog focusing on cultural and sexual themes. She also underwent three years of martial arts training in order to secure roles in action films. In 2017, she hosted on Facebook Live, for the French community website NextPLZ a show about sexuality aimed at youngsters, published a second graphic novel in the DoggyBags collection, and created a YouTube channel dedicated to Sports.

Also in 2017, she made her debut in an action feature film by playing the main villainess in the Cambodian film Jailbreak. Screen Anarchy reviewed her performance positively, commenting that she "displayed tremendous ability to handle the choreography and swordplay" and praising her fight scene with the film's female protagonist, Tharoth Sam.

In 2018, her autobiography, titled Ne dis pas que tu aimes ça (Don't say you like it) was released in France. At the same time, she started working as a publisher for Glénat Editions.