NYPD officers in Brooklyn delivered “ceasefire” warnings to 40 gangbangers in the borough this week as part of the department’s effort to curb violence at the upcoming West Indian American Day parade and J’Ouvert festival.

Dozens of the notices were sent out in the leadup to Monday’s annual festivities in Crown Heights, which has historically been overshadowed by violence, police officials revealed Thursday.

Assistant Chief Charles McEvoy, the commanding officer of Patrol Borough Brooklyn South, “and his team have already done some mitigation factors with some gang members and ceasefire callings — letters sent out,” Chief of Patrol John Chell explained during a press conference.

According to Chell, at least 40 letters were sent out this week alone, just days before scores of revelers were set to swarm the borough to celebrate Caribbean heritage and culture.

The missives to the gang members were meant to offer a simple message: “Hey, be your best behavior,” Chell said.

In another move aimed at deterring crime, Chell said Thursday the NYPD would be placing light towers in areas near the parade route that were plagued by violence in years past.

Paradegoers will need to pass through one of 13 checkpoints set up along Eastern Parkway and they may be subjected to a random search, police officials said.

Thousands of uniformed and undercover officers will also be patrolling the entire city — a tactic the NYPD said helped last year’s Labor Day weekend become the safest on record.

Additionally, the department will deploy drones to survey large, outdoor gatherings and barbeques that might get too rowdy.

“We want everyone to have a celebratory weekend with the least amount of enforcement,” Chell said. “That’s the goal.”