The police force is seen as essential in the push for the protestant Democratic Unionist Party to share the power of government agencies in Ulster, the BBC reported.
Sinn Fein members voted to support the police force in a meeting in Dublin, Ireland after nearly six hours of debate.
Sinn Fein leader Gerry Adams lobbied for the passage of the proposal, calling it essential to fully support the Police Service of Northern Ireland, the BBC said.
"It's bigger than us. It's bigger than Sinn Fein. It's all about the common good," Adams said. "Let us go out of here and ready for the next phase of our struggle."
The BBC said such support from Sinn Fein of policing in Northern Ireland was previously called critical by British Prime Minister Tony Blair and Irish Premier Bertie Ahern.