The incident happened just after 6:30 p.m. Sunday at Little River Park.
The man, 36, has not yet been identified.
Officials said the man swam out to save a child.
He was able to rescue the child but went back under while trying to get ashore.
A rescue team performed CPR for about an hour but was unsuccessful.
Zebulon police chief Timothy Hayworth said this was the first drowning at that spot in at least 18 years.
"This portion of water is not a rapid, not a rough area of water, not a deep area of water and most people come down here to fish or wade out in the water," Hayworth said. "It's not known as a local swimming hole. It's more like a play area. That's what makes it that much more sad. People come here to enjoy their day and relief from the heat and we have a tragedy like this."