Brooklyn Nine-Nine Wiki

This page is about the main antagonist of Season Eight. For other Franks, see Frank (disambiguation).

Frank O'Sullivan is the head of the police union and the main antagonist of Season Eight.


O’Sullivan is very proud of his position and takes his job seriously to the point of being bigoted. He believes that the police, regardless of the circumstance or situation, are always in the right and should not be held accountable for incidents or mistakes. He also believes that “sorry” and “mistake” are the worst things an officer can say.

Throughout the Series[]

Season Eight[]

The Good Ones

O'Sullivan's first appearance, he doesn't allow Jake Peralta and Rosa Diaz to see the bodycam footage of 2 cops who did something wrong to one of Rosa's clients after she became a private investigator.

The Blue Flu

A uniformed officer makes up an incident of a dead mouse in a burrito, which O'Sullivan says was an "Act of political violence by a group of radical, anti-cop, Antifa anarchists working out of the Burrito Haven". He wanted the uniformed officers to get extra hazard pay and for everyone to wear a "Never Forget Burrito" ribbon

The Set-Up

O'Sullivan is suspected of setting up Jake to destroy Amy's NYPD reform program she started. Amy and Rosa try to get him to admit it by taking him to a bar to try to get him drunk to the point where he admits his plan. He manages to outdrink both of them, while they were taking turns, proving an extremely high alcohol tolerance.


On the day of Holt's vow renewals with Kevin, Holt uncovers that O'Sullivan hacked the Compstat system and changed the numbers so it would look like Holt and Amy fudged their numbers in their reform proposal.

Terry meets up with O'Sullivan, who is posing as a Billy Joel superfan and selling memorabilia. To secure his thumbprint, Terry offers 10K for a page of the "original" lyrics of We Didn't Start the Fire, hoping he will refuse due to the amount and give back the paper that he touched which had a resin on it. O'Sullivan surprises them, though, by accepting and giving Terry the money and taking the resin with him. Terry is able to get it back by yelling at him to not allow his entire identity to be wrapped up in another person and to move on.

Despite the squad handing in the evidence that proves that he fudged Compstat number to try and tank the proposal he was re-elected for life despite that not being technically possible.


The 99th Precinct[]

He is frequently at odds with members of the 99th precinct due to his general refusal to allow accountability for police in the union.


  • He is implied to be somewhat homophobic, as he attempted to blackmail both Rosa and Holt by releasing information about their sexuality, unaware that they had already gone public with that information.
  • He is a huge fan of Billy Joel and says, "he taught me everything"
  • He still lives with his mother.
  • He is a fan of the New York Islanders and hosts a YouTube series called "Islanders Talk", discussing whether the NHL can have female hockey fans.
  • He has a very high alcohol tolerance, being able to outdrink both Rosa and Amy despite the two taking turns and even having more drinks the next morning with no signs of being drunk or having a hangover.
  • He can't tell the difference between people of different races.
    • He didn't notice that Rosa and Amy were switching places throughout the night.
    • He didn't recognize Terry when he was out of uniform posing as a superfan.
  • He says that if he is passionate about one thing, it is getting cops off without punishment.
  • He has a mancave with rootbeer on tap.