Robert Lamm was born in Brooklyn, New York and raised in Chicago, Illinois. His parents had a collection of jazz records, which were an early influence on him. He studied art in high school, particularly drawing and painting, but changed direction in college by enrolling in the music program at Roosevelt University in Chicago. In a 2003 interview, Lamm said, "My first musical training came as a member of the choir at Grace Episcopal Church, Brooklyn Heights, New York. It was a very good choir, (Harry Chapin and members of his band were also in this choir at around the same time). It exposed me to some of the great sacred music from the Middle Ages, right up through Bach and into some of the 20th Century composers."
Lamm's first group, known as "The Trondells" formed in 1962 on the South Side of Chicago. "Chicago" was formed in February 1967. In the mid-1990s, Lamm formed a trio with Gerry Beckley of the band America and Carl Wilson of The Beach Boys. After Wilson's death from lung cancer in February 1998, an album was released entitled Like a Brother (2000).
In 2004 Lamm fronted his own group "The Robert Lamm Band", performing concerts in New Zealand and Los Angeles. Apart from his involvement with Chicago, Lamm has recorded a number of solo albums, beginning in 1974 through the present. He also has guest lectured on music production at Stanford University.