After starting his career as a television screenwriter, Cannell created or co-created several dozen successful TV series from the 1970s to the 1990s, often with his creative partner Frank Lupo.

Cannell's creations include The Rockford Files, The A-Team, Renegade, The Greatest American Hero, 21 Jump Street, and The Commish.

[2][3] Cannell struggled with dyslexia in school, but did graduate from the University of Oregon in 1964 with a Bachelor of Science degree in journalism.

[4] The 2009 documentary Dislecksia: The Movie features an interview with Cannell, in which he discusses his struggles with dyslexia and how he managed to be such a successful writer despite his difficulties reading.

During the interview, he mentions how he used to hire typists to overcome his spelling problem, as he refers to his dyslexia, but also describes how he feels his condition has enriched his life.

[citation needed] After college Cannell spent four years working with the family business before selling his first script to the Universal series It Takes a Thief in 1968.

In 1971, he received a telephone call from friend Herman Saunders who was the producer on Jack Webb's police series Adam-12.

He delivered what they wanted in one day, his first full-time gig, and was soon hired as story editor of the series, then in its fourth season, until 1973.

In a 2002 interview, Cannell described his early financial arrangements, saying that at Universal, I signed a deal as a head writer to make $600 a week.

For the first few years, Cannell's office was located on the lot at Paramount Studios in Hollywood, though his earlier work at Universal was still distributed by MCA-Universal.

His first series under his new banner was Tenspeed and Brown Shoe (1980), and was soon followed by The Greatest American Hero (1981–1983), The Quest (1982), The A-Team (1983–1987), Hardcastle and McCormick (1983–1986), Riptide (1984–1986), and Hunter (1984–1991).

[5] In late 1988, Witt/Thomas Productions exited the TeleVentures venture and entered a distribution deal with Walt Disney Television, selling its share to Cannell.

His solution was to build a new, state-of-the-art facility, "The North Shore Studios" on 13 acres with one hundred thousand square feet of office space and seven sound stages.

The series 21 Jump Street was soon followed by J.J. Starbuck (1987–1988), Wiseguy (1987–1990), Unsub (1989), Top of the Hill (1989), Booker (1989–1990), Broken Badges (1990–1991), Palace Guard (1991), Scene of the Crime (1991–1992), The Commish (1991–1996), Street Justice (1991–1993), Silk Stalkings (1991–1999), The Hat Squad (1992–1993), Renegade (1992–1997), Cobra (1993–1994), and Hawkeye (1994–1995).

[8] One of the first shows produced by the newly established Cannell Studios was the short-lived but critically acclaimed corporate drama Profit (1996).

[10] Cannell also acted occasionally, including a recurring role as main antagonist "Dutch" Dixon on his series Renegade.

Actor William Katt, who is an expert musician, wrote a song for Cannell titled "Cody the Cowboy".

According to an episode of Paul Harvey's The Rest of the Story, Cannell frequently had to dictate ideas or even complete scripts with the help of his personal secretary Grace Curcio, an employee of 20 years.