It was first recorded in February 1931 by Ozzie Nelson and also by Wayne King and His Orchestra, with vocal by Ernie Birchill. A popular standard, more than 60 other versions have been recorded, but some of the highest chart ratings were in 1968 by Mama Cass Elliot with The Mamas & the Papas.
“Dream a Little Dream of Me” was recorded for the Mamas & the Papas April 1968 album release The Papas & The Mamas. The group had often sung the song for fun, having been familiarized with it by member Michelle Phillips, whose father had been friends with the song’s co-writer, Fabian Andre, in Mexico City where Michelle Phillips’ family had resided when she was a young girl.
“Mama” Cass Elliot suggested to group leader John Phillips that the group record “Dream a Little Dream of Me”. According to him she was unhappy while recording the song, objecting to its campiness. However, Elliot herself would later tell Melody Maker: “I tried to sing it like it was 1943 and somebody had just come in and said, ‘Here’s a new song.’ I tried to sing it as if it were the first time.” (source Wikipedia)