Edlund was born and raised in Pembroke. He attended Silver Lake Regional High School and was voted by classmates as "Most Artistic" for both the 8th grade and 12th grade yearbook superlatives. At the age of 17, without a driver's license, Edlund was forced to ride with friends and frequent their favorite hangouts. One particular destination, the New England Comics store, spawned Edlund's interest in the comic book medium, which later launched his art and writing career.

Creation of The Tick

While still in high school, he began developing his satirical superhero, The Tick, who became the mascot of the New England Comics newsletter. Edlund was offered to create a comic book series based on the character by New England Comics when, due to a production mix-up, the publisher needed a new title fast. Edlund graduated from high school in 1986 and continued to draw his popular character while majoring in film at Massachusetts College of Art. The debut issue of The Tick took a year and a half for Edlund to develop.

While still in college, Edlund was approached by Kiscom, a New Jersey-based toy licensing and design company, who wanted to develop merchandising off The Tick much like the successful Teenage Mutant Ninja Turtles a year prior. However, no big television network was willing to take the concept of a Tick animated series. Finally, Sunbow Entertainment, a small New York-based animation company, paired Edlund up with writer Richard Libmann-Smith. After having their premiere episode turned down by FOX, the duo worked tirelessly and got approval with a refined version.

In 1994, The Tick debuted as an animated series on FOX and lasted three seasons. The program led to various toy and merchandising deals, and although this did not reach the phenomenon of the Ninja Turtles franchise, Edlund expressed content in his character as a "much more sincere proposal." The Tick appeared on the FOX network in late 2001 with a short-lived live-action series.

In the late 1990s, Edlund collaborated with indie filmmaker Lisa Hammer and her husband, Eric Hammer, on the film Crawley. The Hammers would later work with Edlund again during the creation of The Venture Bros. which draws inspiration from The Tick.

In the 2000s, he was employed by Joss Whedon at Mutant Enemy, first on Firefly and then later on the final seasons of Angel, writing and directing the Hugo Award nominated episode, "Smile Time." Edlund credits Whedon with his education on creating character arcs for television. Edlund also had a hand in creating characters for Whedon's successful web-series Doctor Horrible's Sing-Along Blog which he contributed "Bad Horse" and the henchman sidekick "Moist."

In 2005, Edlund served as co-executive producer on Point Pleasant in 2005. He also wrote the The Clone Wars second season episode "Grievous Intrigue". He is currently executive producer and writer on the TV series Supernatural.