Kreisberg graduated from the Boston University College of Communication in 1993.
His first job was on the short-lived animated sitcom Mission Hill. He has written for several other series including: Justice League, The Simpsons, Hope & Faith, Boston Legal, Lipstick Jungle, Eli Stone, The Vampire Diaries, Star Wars: The Clone Wars, My Family, and Warehouse 13.
In November 2015, Kreisberg signed a multi-year deal with Warner Bros. Television, in which he will continue to develop new projects as well as remain the sole showrunner of The Flash, co-showrunner of Supergirl (along with Ali Adler), and executive producer on Arrow and Legends of Tomorrow.
In 2009, he joined the FOX science-fiction/horror series Fringe as a co-executive producer and writer. At the end of season one, Kreisberg left the show. He co-wrote the following episodes:"Midnight" (01.18) (co-written with co-executive producer J.H. Wyman)
"Unearthed" (02.11) (co-written with co-executive producer David H. Goodman)
In 2011, Kreisberg was hired to write a pilot based on DC Comics hero Booster Gold, for Syfy. The script has gone through many iterations and is said to still be in consideration at the network.
In 2011, Kreisberg, Marc Guggenheim, and Greg Berlanti began developing Arrow, a re-imagining of the DC Comics comic book character, Green Arrow, for The CW. In January 2012, The CW picked the project up to pilot. On January 31, 2012, actor Stephen Amell was cast in the title role of Oliver Queen/Arrow. On May 11, 2012, The CW officially picked Arrow up to series. It premiered on October 10, 2012.
In July 2013, it was announced that Kreisberg, fellow Arrow co-creator Berlanti and DC Comics CCO Geoff Johns would be introducing Barry Allen during the shows sophomore year, with the 20th episode serving as a backdoor pilot. Actor Grant Gustin was cast and first appeared in episode 208, "The Scientist". CW brass were so pleased with the handling of the character that they greenlit a full-fledged pilot, foregoing the backdoor version. In May 2014, The Flash was officially ordered to series. It premiered October 7, 2014, to critical and public acclaim.
On February 26, 2015, it was announced that Kreisberg, along with Guggenheim and Berlanti, would write/executive produce a spin-off series featuring The Atom/Brandon Routh, Captain Cold/Wentworth Miller, Martin Stein/Victor Garber, and Caity Lotz, for a potential 2016 premiere.
Kreisberg has written the comic book series Green Arrow and Black Canary, Batman Confidential
In 2008, Arcana Comics began publishing Helen Killer, a comic book by Kreisberg with art by Matthew Rice. In it, a college-aged Helen Keller is given a device which allows her to see and hear and which increases her physical abilities, at which point she is hired to protect the President of the United States.
It was announced in July 2014, that Kreisberg and Arrow executive story editor Ben Sokolowski would be taking over the Green Arrow title in October of that year, beginning with issue #35.