Angel Baldwin, 12, and his sister Carina Baldwin, 10, allegedly witnessed Ashley Turner steal their mother's purse near the Daytona Beach pier Sunday, police said.
The siblings took off after Turner, chasing her across the beach.
"I kept saying give me my mom's purse back, and she kept saying 'I have no idea what you're talking about,'" Angel Baldwin told Orlando's WFTV.
There were also two men with Turner, police said.
"He said you are lucky you are a little kid or I would mess you up," Angel said one of the men told him.
The children kept running and Carina chased Turner into the bathroom of a nearby store, where the suspect left the purse and ran.
Police caught up with Turner and arrested her, but said they didn't have enough evidence to charge the two men seen with Turner.
"I'm very proud of them, but I did have a stern talk with them never to do this again ... . Next time you call for help!" said the children's mother Angela Baldwin.