Having been on the verge of completing his move to the Parc des Princes in the last few weeks, the ex-Athletic Club man has now agreed terms with the Ligue 1 champions.
Herrera is a free agent in June after United failed to convince him to sign a new contact at Old Trafford.
And the Spaniard will now be turning out for PSG next term, with the length of his deal the only thing left to be finalised.
Herrera is thought to been on a five-year contract, but he may yet agree to sign for four years.
Athletic Club attempted to recapture their former midfielder, but negotiations with PSG were in the advanced stage by the time they made their interest known.
Herrera has made 187 appearances for United since joining the club in 2014, winning an FA Cup, a League Cup and the Europa League.
5 things Manchester United must do to move forward as a club