Officials tightened security and moved the starting time to 6 a.m. Officers were patting down revelers, vendors and residents hours before that.
The West Indian Day Parade along Eastern Parkway followed the festival.
Thousands of revelers, including musicians, dancers and costumed troupes, gathered Monday for the morning celebration and the afternoon parade.
This year, revelers had to enter the route along 12 designated entry points and had to pass through metal detectors. No alcohol or backpacks were allowed.
300 additional officers were on patrol and policed party areas outside the barriers.
Some participants said security was so strict that fewer people turned out for the festival this year.
"I think they should come up with a better strategy of keeping people safe. This isn't keeping people safe, it's deterring people from experiencing the culture," said J'ouvert participant Nadira Byles.
Despite the security, one man was shot just before 5 p.m. Monday. It happened along the parade route on Eastern Parkway between Brooklyn Avenue and New York Avenue. Their injuries were said to be serious but non-life threatening.
Three people were shot overnight near Eastern Parkway, but police say that shooting is not connected to the celebration.
Two people were killed last year, despite an increased police presence and more lighting, and in 2015, an aide to Gov. Andrew Cuomo named Carey Gabay was shot and killed.
One of the victims was 22-year-old Tiarah Poyau, a student at St. John's University. A 17-year was also shot and killed.
Gabay, a 43-year-old lawyer who had worked for Cuomo and was deputy counsel of the state's economic development agency, was shot in the head as two street gangs exchanged gunfire.
The name J'ouvert means daybreak, put together from the French words "jour" and "ouvert." It is the start of a carnival that includes the separate New York Caribbean Carnival Parade later Monday featuring "pretty mas," or masquerade, revelers in giant feathery costumes riding on bright floats.
J'ouvert's costumes, called "ole mas," are different but just as wild. Some people dress in rags and don helmets with giant horns painted a thick-as-molasses black. Others cover themselves in red paint or black oil. The costumes are a nod to the original celebrations that began in Trinidad in the mid-1800s when slaves were emancipated.
(The Associated Press contributed to this report.)