Attah joins on a free transfer after leaving fellow top-flight side Elmina Sharks where he was a dependable pair of hands.
Duration and terms of his move to the capital club remain undisclosed.
A club statement read: ''The Hearts of Oak management is delighted to announce the signing of goalkeeper Richard Attah. He has signed a long term deal with the club.''
Attah will have to battle for the No.1 spot with Richmond Ayi and Ben Mensah.
The 24year former Elimina Sharks stopper reunites with Hearts of Coach Kim Grant,who was Technical Director for the Sharks in 2017.
Attah will be looking forward to a successful GPL season with the Rainbow club.