The Stooges awake in the middle of the night to a crying baby left on their doorstep. A letter from the despondent mother (Julie Gibson) states that baby Jimmie (Joyce Gardner) has been abandoned. The Stooges react by taking the little guy in, feeding him, and trying their best to act fatherly.
When the mother and two motorcycle cops come to reclaim the baby the Stooges evacuate their home quickly, with Jimmie in tow; unbeknownst to the stooges Jimmie crawled into the back seat of their car. The police on their motorcycles track them down and the baby is returned to the parents who, the father being one of the cops, reconcile. The Stooges, meanwhile, make a conspicuous escape by skittering away hidden in large haystacks.
- Moe Howard as Moe
- Larry Fine as Larry
- Curly Howard as Curly
- Julie Gibson as Mrs. Collins
- Bud Jamison as Pete
- Joyce Gardner as Jimmie Collins
- Clarence Straight as Sam Collins
- Dudley Dickerson as Roadside Worker
- Filming for Sock-a-Bye Baby commenced between April 28 and May 1, 1942.
- The film title is a parody of the lullaby "Rock-a-bye Baby".