With an ensemble that includes Jaime Pressly, Mimi Kennedy, Beth Hall and William Fichtner, the show is about two generations of a family recovering from substance-abuse problems.
Season 5 is airing now on CBS Thursdays. Season 6 is to air in 2018-19.
"Mom has been a lynchpin comedy for us over the last several years," Kelly Kahl, president of CBS Entertainment, said in a statement. "It's a fearless series that tackles provocative social issues with laughter and grace, and a large, loyal audience has followed. With gifted talents like Anna and Allison leading a great ensemble cast, and a production team headed by Chuck Lorre, Eddie Gorodetsky, Nick Bakay and Gemma Baker, this series just keeps getting better."