Animation

Timm's early career in animation was varied; he started at Filmation, working on the layout of Blackstar, Flash Gordon, He-Man and the Masters of the Universe, and The Lone Ranger (Timm also did background work on G.I. Joe). He also worked for numerous other employers, including Ralph Bakshi, Don Bluth Productions, and attempted to find work at Marvel Comics and DC Comics, but without luck. In 1989, Timm joined Warner Bros. At Warner, Timm worked on Tiny Toon Adventures.

However, Timm is best known for his subsequent work on the animated series based on various DC Comics superheroes, popularly referred to as the "DCAU" (DC animated universe). Along with his Tiny Toons partner Eric Radomski, Timm co-created and produced The Animated Series, which premiered in September 5, 1992, and went on to co-create and produce The Animated Series (premiered in September 1996), The New Batman Adventures (premiered in September 1997), and Batman Beyond (premiered in January 1999). He also served as producer on the feature-length Return of the Joker before taking the helm as creator and producer of the animated version of Justice League, which debuted in November 2001. This series continued in the form of Justice League Unlimited. Timm actually had very little to do with the production of the Teen Titans animated series, though because of a mistake in the first season end credits he is often mistaken for an executive producer. Timm was also the producer and co-director of the direct-to-video Superman Doomsday.

DC universe animated series, including Justice League, Justice League Unlimited, Batman Beyond, and other DC-set works associated with Timm (and his collaborators') art styles are often referred to by fans as "The Timmverse" of DC comics, relating to those series' distillation of popular storylines from the comic book versions or the outright introduction of new characters or relationships (such as Harley Quinn, alterations to The Question's personality and background, or Batman and Wonder Woman's romantic fling).

His 2008 project Gotham Knight is a departure from the "Timmverse" style, with Timm in a producer role collaborating with Japanese animators on a direct-to-DVD anthology that takes place between Batman Begins and The Dark Knight.

Acting

Though Timm does not usually work as an actor, he has played several characters in the animated series he has been involved in. His cameos include the episode of The Animated Series, "Beware the Gray Ghost", playing the toy shop owner, as himself in the episode of The New Batman Adventures, "Holiday Knights", and also as the leader of the Jokerz gang in Batman Beyond, which he joked he did under duress and also joked was 'Emmy-Award Winning material'. More recently, he appeared in an animated form in The Brave and the Bold episode Legends of the Dark Mite in a comic book convention parody scene, where he was wearing Joker's costume, along with Paul Dini wearing Harley Quinn's costume. Prior to that he was animated in The Batman, appearing as a mental patient in Arkham. He has also played a guard in the direct-to-video animated film, Return of the Joker.Most recently, Bruce Timm makes a cameo appearance in First Flight as Bug Boy and played The Riddler in Under the Red Hood.

Comics

While Timm is known primarily for his work in animation, his first ambition was to become a comic-book artist. Although this dream did not materialize, leading him to a life in animation, Timm nevertheless produced several one-shots and miniseries, mostly for DC Comics.

In 1994, Timm and writer Paul Dini won the Eisner Award for Best Single Story for Batman Adventures: Mad Love. Timm won the same prize the next year as well, for Batman Adventures Holiday Special, (a one-shot with several Christmas-themed stories) with Dini, Ronnie del Carmen and others. Later, Timm was involved with Batman Adventures and has also worked on Avengers and Vampirella. He is also a popular cover and pin-up artist.

In 2000, he did the art for an issue of DC's Vertigo imprint horror title, Flinch

Bruce Timm co-created Harley Quinn, (with writer Paul Dini) working from Dini's original design. Harley's popularity on television led to her inclusion in the mainstream DC Universe. In 2004, Timm and Dini (assisted by Shane Glines as inker) released a three-issue Harley and Ivy miniseries, which was in the works for years.

Timm also drew the 1999 "Avengers 1½" special for Marvel Comics, written by Roger Stern.

In 2005, Timm contributed artwork for two comics. One was a short story in Conan #18, titled "Conan's Favorite Joke". The other was a Black Canary short story in Birds of Prey #86.

In 2008, he provided the art work for a short 2 page Harley Quinn origin story for Paul Dini's countdown.

Timm's minimalist, angular style is heavily based in his love of 1950s and 1960s-era comics and art deco architecture style. He is also completely self-taught, having never received any formal art schooling.

He lists his artistic influences as Jack Kirby, Harvey Kurtzman, Jim Steranko, John Buscema, Wally Wood, Frank Frazetta, Dan DeCarlo, and Alex Toth.

Although he shared character designer duties on The Animated Series and Justice League with James Tucker, Timm did virtually all the original character designs for The Animated Series himself (with the exceptions of Mr. Freeze and the Riddler, who were designed by Mike Mignola and the characters Man Bat & the Mad Hatter, who were designed by Kevin Nowlan).