The dead included one US national, a Canadian, an Italian and two Mexican nationals.
The shooting broke out at an electronic music festival that had drawn visitors from around the world to the beach resort city.
Video of the aftermath posted on social media showed frantic clubgoers rushing into the street as rescuers arrived.
Canadian Kirk Wilson, a safety supervisor for the festival, and Daniel Pessina, from Italy, a BPM staff member, were among the dead. Rafael Antonio Penaloza, from Mexico, died at a hospital and another Mexican, Geovanni Francisco Ruiz Murillo also died in the incident.
American Alejandra Margarita Villanueva Ibarra was the fifth victim, according to a representative from the state attorney's office in Quintana Roo, speaking on condition of anonymity.
Earlier information from state prosecutor Miguel Angel Pech Cen had indicated two Canadians were among the dead.
A Taurus .38 caliber revolver was recovered at the scene by police. A total of 20 bullet shells were found.
The US Embassy in Mexico put out a statement that it is aware of the US citizen who died in the attack.
'Everyone started screaming'
Jake Lubell said he was outside the Blue Parrot when he heard gunshots. "People around me were running. There was a lot of screaming," he said. "Gunshots went on for roughly 30 seconds."
"I heard what sounded like firecrackers. Everyone started screaming and running for cover," said Andrew Badecker, who was outside the Blue Parrot club when the shooting began.
People climbed over a fence behind the club to escape, the professional poker player said.
"I was trying to help people over," he said. "I was worried someone would get trampled."
In fact, a woman died in a stampede of people rushing out of the club, the state prosecutor said.
Several victims were found dead on the beach outside, he said.
Playa del Carmen, about 40 miles (64 kilometers) south of Cancun, is a popular destination for tourists from Mexico and around the world.
It's located in Mexico's Quintana Roo state, which has maintained a reputation as a safe travel destination
even as other parts of the country have struggled to deal with drug-related violence.
'We are overcome with grief'
Of the 15 people injured, seven remained hospitalized Monday morning, Pech Cen said. Authorities haven't released the nationalities of all the victims. Five Mexicans, four Americans, two Canadians and a Colombian were listed among the wounded.
On a Facebook page for The BPM Festival
, a 10-day electronic music event that was closing Monday, organizers said a lone shooter had opened fire in front of the Blue Parrot. Three members of the event's security team were killed trying to protect patrons inside, the festival said.
"We are overcome with grief over this senseless act of violence and we are cooperating fully with local law enforcement and government officials as they continue their investigation," the festival statement reads.
Authorities interrogating three people
Authorities in Quintana Roo say they're still trying to determine who was behind the shooting -- and why it occurred.
A preliminary investigation indicates that the shootout began when members of event security tried to stop a person who entered the club with a firearm, Pech Cen said.
Authorities are interrogating three people, the state prosecutor said, but it's unclear whether they were involved in the shooting.