He joined from Newcastle Falcons after for the duration of the Rugby World Cup, subject to medical.
He made 55 appearances for Harlequins over four seasons at Twickenham Stoop and was part of the squad which won the Aviva Premiership title in 2012.
The 25-year-old, who was born in Hannover, has had two stints with Newcastle Falcons – making 50 appearances for the Aviva Premiership side.
He has represented England Saxons and England U20s.