The shooting happened around 2:50 p.m. on the 1100 block of Cornelia Street.
Police responded to the area for multiple calls about a drive-by shooting, and they also were called to a local hospital for a youth with a gunshot wound.
The boy was struck by a single shot to his shoulder, police said, and he was listed in stable condition.
Police believe the shooting was gang-related and the boy was not the intended target.
Anyone with information is asked to call the Pomona Police Department at 909-620-2085.
Anonymous information can be provided to Crime Stoppers by calling (800) 222-TIPS (8477), using your smartphone by downloading the "P3 Tips" Mobile APP on Google play or the Apple Store or by using the Crime Stoppers website.