Weisman is a former English composition and writing teacher and received degrees at Stanford University and USC. During an interview done during Comic-Con International 2010, Weisman revealed that while 22 years old, he wrote a four issue mini-series for DC Comics starring the superheroine Black Canary. The first issue of the series was pencilled, but the project was ultimately shelved due to the character being used in writer/artist Mike Grell's high profile The Longbow Hunters series. Elements from the ill-fated project were used for his upcoming DC Showcase: Green Arrow short film.

In addition to developing and showrunning the popular series Gargoyles, the second season of W.I.T.C.H. and The Spectacular Spider-Man, Weisman has written for numerous animated series, including The Series, Starship Troopers Chronicles, and Kim Possible. Weisman wrote the series bible for Max Steel and produced the show's first season. Weisman voice directs and voice acts on occasion; he played the role of Donald Menken on The Spectacular Spider-Man.

Weisman is notable for the question and answer forum he participates in with Gargoyles fans online, often revealing his intended plans for the show.

Weisman has also written for comics, including Gargoyles, a continuation of the storyline from the television series. Weisman was not new to comics, having spent time at DC as an editor and co-writing Captain Atom with Cary Bates. A parody of Gargoyles later appeared in a Weisman-penned story in JLA Showcase #1.

Weisman has written episodes for the following TV shows:

• Jem
• "Video Wars"
• Buzz Lightyear of Star Command
• "Star Crossed"
• "The Clone Rangers"
• The Big Guy and Rusty the Boy Robot
• "Out of Whack"
• Max Steel
• "Shadows"
• Starship Troopers Chronicles
• "Funeral for a Friend"
• "Liquid Dreams"
• Milo's Return
• "The Last" (He also voice directed Atlantis 2)
• Kim Possible
• "Queen Bebe"
• "Big Bother"
• Super Robot Monkey Team Hyperforce Go!
• "The Circus of Ooze"
• "The Hunt for The Citadel of Bone"
• The Batman
• "The Big Chill"
• "The Rubber Face of Comedy Part 1"
• "The Clayface of Tragedy Part 2"
• "Meltdown"
• "Strange Minds"
• "The Everywhere Man"
• "Artifacts"
• The Series
• "The Elle of My Dreams Syndrome" (A.K.A. The Big Sleep Syndrome)
• "The Black Guard Syndrome" (co-written with his brother, Jon Weisman)
• "The Big Bad Bug Syndrome"
• "The Star System Syndrome"
• Ben 10
• "Ben 10,000"
• "Under Wraps"
• "Ken 10"
• Legion of Super Heroes
• "Man From the Edge of Tomorrow, Part 2"
• The Brave and the Bold
• "Death Race to Oblivion!"
• "Requiem for a Scarlet Speedster!"