Parker went to Berklee College of Music in Boston before transferring to the University of Colorado in Boulder, where he met Matt Stone. He was majoring in music, and, with a goal to someday score films, took classes to learn more about the film process. He made several animated shorts including American History which won a Student Academy Award, and The Spirit of Christmas: Jesus vs. Frosty with Stone.

Parker's first live action film was a feature length piece about Alferd Packer, a Colorado miner who was the first person convicted of cannibalism in America. A trailer was shot over the summer, and was used to help raise enough funds to shoot the film. Alferd Packer, The Musical (it was renamed Cannibal! The Musical when picked up in 1996 for distribution by Troma) began filming during spring break in 1993. However, Lloyd Kaufman, president of Troma, wanted to name it Fudge Packer, the Musical. Family, friends and fellow students all took part in the film. Students who participated received intern credit. Parker, however, was expelled due to excessive absences while filming, and did not go on to graduate. (Source-http://treyparker.info/biography.htm)

Parker's college film caught the eye of Brian Graden, a then Fox executive. In 1995, Graden commissioned Stone and Parker to create a video Christmas card based on their animated college short. The Spirit of Christmas: Jesus vs. Santa was the result -- a five minute short that featured an uncensored Stan Marsh, Kyle Broflovski, Eric Cartman and Kenny McCormick watching Jesus and Santa battle it out for ownership of Christmas. One of the recipients of the video (rumored to be George Clooney) made several hundred copies, and the animation became a must-see passed around Hollywood and the Internet.

That same year, Parker created a pilot for Fox called Time Warped -- a "musical romp through time" featuring a story about Aaron and Moses. Fox felt the idea would work better as a children's show so a new pilot, Rom & Jul was made for Fox Kids -- a Romeo and Juliet-esque story about a Homo erectus and Australopithecus who fall in love despite the conflict between their species. Fox Kids passed on the show.

Parker wrote, directed and starred in his second feature film Orgazmo in 1997, about a wholesome Mormon who becomes a celebrity in the Los Angeles' adult film world. Due to the NC-17 rating given by the Motion Picture Association of America it did not have a wide release.

Parker and Stone were hired by Comedy Central to create a show based on the animated characters they created in college. Though it didn't test well with audiences, Comedy Central decided to pick it up for six episodes anyway. South Park made its debut on August 13, 1997, and has since gone on to be the highest rated original series in the network's history.

In 1998, Parker starred with Stone, Dian Bachar and Yasmine Bleeth in BASEketball, directed by David Zucker of Airplane! and Naked Gun fame. The story follows a group of friends who take their homemade game from neighborhood driveways to the professional sports world.

In the summer of 1999, Parker and Stone released their critically acclaimed feature length film, South Park: Bigger, Longer & Uncut, which was, naturally, a musical. "Blame Canada", a song written by Parker and Marc Shaiman, was nominated for Best Song at the Academy Awards. The award was lost to Phil Collins, who was spoofed in later episodes of South Park.

After a contract renegotiation in 2000, three more seasons were added to South Park and Parker and Stone had a deal to create a live action sitcom. In 2001, That's My Bush! premiered (it was a sitcom that portrayed the Commander in Chief as the lovable main character). It was not brought back for a second season due to its high costs (reportedly $700,000 per episode) and meager ratings. Another contract negotiation in 2003 picked up South Park for a ninth season, with an option to pick up a tenth.

Team America: World Police, the most recent creation from the duo, is a marionette movie about a special police force dedicated to saving the world from terrorists, and was released in October 2004.

Parker and his partner, Matt Stone, have received criticism and acclaim from both sides of the political spectrum, making them hard to pin down politically, except that they display irreverence for almost any authority figure. The term South Park Republican has been coined to refer to those who claim that South Park reflects a Republican, although non-traditional, viewpoint. Historically, though, Parker has described himself as "middle-ground", and he is a registered member of the United States Libertarian Party.

On September 9, 2005, Comedy Central struck a deal with Parker and Stone for three more seasons of the show. The network has committed to 42 episodes (including those of the second half of season 9), or three more seasons, of South Park over the next three years, which means that the show will run till 2009. Parker and Stone will continue to write, direct and edit every episode of the show. The order brings the series total to 182 episodes. A sanitized version of South Park bowed in syndication on September 19.

In addition to currently working on the tenth season of South Park, there is talk that Parker and Stone are creating a stage musical with Avenue Q creators Robert Lopez and Jeff Marx. They also have plans to form a production company, possibly with Paramount. As for the prospect of making more films, Parker is not enthusiastic, for the time being: "Team America almost killed us. We'd like to figure out a way to do our own movies, but not die doing them, and maybe help some other people produce their movies, like graduate to the next level because we are getting up there in age." .

Contrary to his comments on November 14, Parker and Stone have signed a three-year production deal with Paramount Pictures. They named their new banner Trunity, a Mediar company, a division of True Mediar, a Unity Corpbopoly. Paramount and Comedy Central are both owned by Viacom, and will continue to be housed under the same umbrella when the parent company splits into two entities by year's end (2005).