PSG has moved to secure the signatures of the France internationals, both of whom have penned three-year contracts with the Parc des Princes outfit.
PSG has not disclosed any details of the transfers, but the players penned three-year deals.
The move for Menez was long in the pipeline after Olympique Marseille pulled out of the race to sign the France international.
Menez was given permission to leave Roma's preseason training on Sunday in anticipation of the transfer going through. The 24-year-old moves back to France having previously played for Sochaux and Monaco.
Matuidi joins from Saint Etienne having spent four years with the Stade Geoffroy-Guichard-based outfit.