In the video, the baby appears limp as she struggles for air, and begins turning blue.
Warning the video may be difficult to watch for some viewers.
Kimbro laid the child on her mother's lap and searched for a pulse, then began tapping on her chest to clear her airway and massaging her heart.
"Come on baby, cry for me. Cry for me," the deputy says in the video. "Come on, open those eyes sweetheart."
Seconds later, the breakthrough came as the baby starts to cry.
"There we go. As long as she's crying like that, she's breathing," Kimbro said.
The deputy kept working on Riley for another five minutes until paramedics arrived.
The Berkeley County Sheriff's Office, which awarded Kimbro a life-saving medal for his heroic actions, said the baby is alive and healthy.