The men were shot in the parking lot of David's Cafe II near Miami Beach's Lincoln Road around 5:30 a.m., said restaurant manager Bertha Handevadt.
One died at the scene and the other shortly after being taken to a hospital, Miami Beach police spokesman Sgt. Bobby Hernandez said. Both were in their 20s, and at least one was from Orlando.
Authorities do not know what sparked the gunfire outside the restaurant, where tourists and other revelers were having a last snack and early risers were grabbing breakfast.
Eight people were taken into custody. Four were at the scene and claimed to be the victims' friends but later changed their story and were not cooperating with police, Hernandez said.
Four others were brought in after police caught up with their silver Mercedes on the MacArthur Causeway, which links Miami Beach with downtown Miami.
"One of the occupants jumped out and was seen going over an embankment and trying to hide," Hernandez said.
Authorities caught him and were interviewing all eight, he said.
In recent years, Miami Beach has drawn thousands of fans of hip-hop music over the Memorial Day weekend for concerts and other events.
At least 600 people had been arrested since Thursday morning, police said. More than 1,000 were arrested during the same weekend last year, mostly for misdemeanors.