Troy Davis, 38, faced execution today before the decision by the board after less than an hour of deliberation.
The stay means the execution will be on hold while the board weighs evidence presented as part of the request for clemency.
Earlier Monday, lawyers for Mr. Davis spent more than five hours pleading with the board to grant a reprieve to their client.
Prosecutors were given a chance during the closed-door hearing to rebut the request for clemency for Mr. Davis, who was scheduled to be executed at 7 p.m. today for the Aug. 19, 1989, murder of Officer Mark MacPhail.
The board's options included commuting Mr. Davis' death sentence to life in prison or granting a stay of his execution while it considers the issues.
"We are no longer under the gun and we can present the rest of our innocence case," Mr. Davis' lawyer Jason Ewart said after the board's decision.
The officer's widow, Joan MacPhail, said in an interview that she was disappointed by the decision.
"I believe they are setting a precedent for all criminals that it is perfectly fine to kill a cop and get away with it," she said.
Among those who argued for clemency for Mr. Davis were friends, family and U.S. Rep. John Lewis, an Atlanta Democrat and civil rights icon. Five witnesses who testified at trial spoke on Mr. Davis' behalf, Mr. Ewart said.
Among those present for the state at the parole board's offices were the victim's widow and mother, and the district attorney for Chatham County. They have argued that Mr. Davis received a fair trial and has had plenty of appeals, all of which have failed.
"I believe police did their job correctly and found the right man," the slain officer's son, Mark MacPhail Jr., told reporters after his family addressed the board.
The younger Mr. MacPhail, now 18, said he told the board what it was like to grow up without a father.
A jury convicted Mr. Davis, 38, for the murder of Mr. MacPhail, 27, who was shot twice after he rushed to help a homeless man who had been assaulted.
The shooting took place in a Burger King parking lot next to the bus station where Mr. MacPhail worked off-duty as a security guard.
Lawyers said seven of nine witnesses who testified that they either saw Mr. Davis shoot the officer, saw him assault the homeless man before the shooting or heard Mr. Davis confess to the slaying have recanted or contradicted their testimony.
But Mrs. MacPhail said police arrested the right man.
"By making us wait, it's another sock in the stomach," she said. "It's tearing us up."