Cheech and Chong, while one of the most successful comedy acts of all time, experienced creative differences and split in 1985. This was devastating to Chong. To him, Cheech was "closer than a wife. The only thing we didn't do was have sex." Of their split, he says, "It was like a death in the family. I don't know if I'll ever get over it."

Before branching out into film, Chong was a guitarist and songwriter for Motown band Bobby Taylor & the Vancouvers, briefly featuring a very young Jimi Hendrix . Among his compositions for the group were "Does Your Mama Know About Me", which hit #29 on the United States pop chart and #5 on the US R&B chart.

In the late 1980s, Chong became a naturalized citizen of the United States.

Chong was a recurring character and later a regular character as the hippie "Leo" during the second, third, fourth, seventh, and eighth seasons of That '70s Show.

Chong has an unabashed love of marijuana, saying, "I get high constantly. If you smoke pot, eat well and work out, I guarantee you'll live forever."

In 2003, Chong was one of those targeted by two American investigations code-named Operation Pipe Dreams and Operation Headhunter, which sought out businesses selling drug paraphernalia, mostly marijuana pipes. He was charged for his part in financing and promoting Chong Glass/Nice Dreams, a company started by his son Paris. Chong agreed to plead guilty to one count of conspiracy to distribute drug paraphernalia in exchange for non-prosecution of his wife, Shelby, and his son.

While most of the approximately 55 individuals charged as a result of the operations were sentenced to fines and home detentions, Chong was sentenced on September 11, 2003, to 9 months in a federal prison, forfeiture of $103,000, and a year of probation.

While government officials denied that Chong was treated any differently from the other defendants, many felt that he was made an example of by the government. Soon afterwards, marijuana advocates started the Free Tommy Chong! movement that called for his release.

Chong served his sentence from October 8, 2003 to July 7, 2004, and in December 2004 was to appear off-Broadway in a one-man show entitled "The Marijuana-Logues", a parody of Eve Ensler's The Vagina Monologues. His legal concerns, including that audiences were actually smoking marijuana in some of the shows early in its tour ultimately caused him to quit the show.

In 2005, Chong returned to his role as Leo on That '70s Show.

In September of 2005 a/k/a Tommy Chong premiered at the Toronto International Film Festival. The documentary, directed by Josh Gilbert, chronicles Chong's recent legal troubles and features interviews with Cheech Marin, Bill Maher, Lou Adler, Eric Schlosser and Jay Leno.