Marin graduated from Bishop Alemany High School and then studied English at San Fernando Valley State College (now California State University, Northridge), where he was a member of Phi Sigma Kappa and graduated in 1968. Marin then auditioned to sing for Frank Zappa in 1967, but instead moved to Vancouver, British Columbia in September to dodge the draft during the Vietnam War. Marin met his future comedic partner, Tommy Chong, in Calgary, Alberta.

Marin was married in 1975 to Darlene Morley, who co-produced Cheech & Chong’s The Corsican Brothers and also played minor roles in earlier Cheech & Chong films under the name Rikki Marin. The couple had one child and divorced in 1984. Marin married artist Patti Heid in 1986; they had two children and have since divorced. Marin married his longtime girlfriend, Russian pianist Natasha Rubin, on August 8, 2009, in a sunset ceremony at their home.

After Cheech & Chong disbanded in 1985, Marin starred in a number of films as a solo actor, most notably Born in East L.A., The Shrimp on the Barbie, Tin Cup, and Once Upon a Time in Mexico. He made a cameo appearance as a dockworker in Ghostbusters II. In 2004 he made his second appearance as a policeman, as “Officer Salino” in the film adaptation of John Grisham’s holiday novel “Skipping Christmas”, under the title “Christmas With the Kranks”, starring Tim Allen and Jamie Lee Curtis. Marin appeared in the Fox sitcom Married… with Children as the voice of the Bundy’s Briard dog, Buck; he voiced the character in three episodes: Look Who’s Barking, Change for a Buck and Assault and Batteries.

In 2005, Marin lent his voice to the animated children’s series Dora the Explorer. He appeared in the episode “A Crown for King Juan el Bobo”, as the Puerto Rican folk hero Juan Bobo.

In late 2006, Marin participated in Simon Cowell’s Celebrity Duets, having sung with Peter Frampton, Randy Travis, Clint Black, Aaron Neville, and Al Jarreau. He was the fourth to be eliminated. In that same year, he voiced as Gaspar Gomez in Scarface: The World Is Yours.

Marin has released two best-selling albums in the children’s music genre, My Name is Cheech, the School Bus Driver (1992) and My Name is Cheech, The School Bus Driver “Coast to Coast” (1997). Both albums were released bilingually. In July 2007, the book Cheech the School Bus Driver was released, written by Marin, illustrated by Orlando L. Ramirez, and published by HarperCollins.

In 2009, he appeared in the Hallmark Channel movie Expecting a Miracle.

He was a co-host for WWE Raw on March 1, 2010, with his comedy partner Tommy Chong, in Oklahoma City.

On March 18, 2010, Marin beat journalist Anderson Cooper and actress Aisha Tyler on Celebrity Jeopardy!’s Million Dollar Celebrity Invitational. Cooper admitted he was “crushed” by Marin. Marin also won his semifinal round early May but lost in the May 6–7 final to Michael McKean. He had previously won the first Celebrity Jeopardy! tournament in 1992.

In January 2012, he was one of eight celebrities participating in the Food Network reality series Rachael vs. Guy: Celebrity Cook-Off. He was eliminated on the third week of the competition.

Marin’s nickname “Cheech” is short for “chicharron”, fried pork rind, which is a popular snack and ingredient in Latin American cuisine. In a 2017 NPR interview, Marin attributed the nickname to his uncle: “I came home from the hospital, I was like a couple days old or something, my uncle came over and he looked in the crib and he said [in Spanish], ‘Ay, parece un chicharrón.’ Looks like a little chicharrón, you know?”

On April 19, 2018, Cheech (as part of GLE Brands Inc) signed an agreement with Heritage Cannabis Holdings Corporation (CSE: CANN) to have exclusive rights to use cannabis and cannabis related products utilizing the Private Stash brand throughout Canada for a period of 2 years, with the agreement automatically renewing for an additional year upon achieving various milestones.

On June 25, 2019, The New York Times Magazine listed Cheech & Chong among hundreds of artists whose material was reportedly destroyed in the 2008 Universal fire.