The 25-year-old makes his return to the Primeira Liga -having left Rio Ave during the January transfer window- by signing a three-year deal which will see him at the side until 2020.
Wakaso leaves Lorient having made 11 appearances as they were relegated to Ligue 2 after losing a relegation play-off tie to Troyes.
Pedro Martins is looking strengthen his side ahead of their Europa League campaign after finishing fourth in the Primeira Liga last campaign.
Wakaso’s arrival at the club could also mean that South African midfielder – Bongani Zungu , who has been linked with a move away from the club could well be allowed to leave.
Zungu has been linked with a move away from Os Vimaranenses all summer with English and French sides believed to be after his signature.