The brother of former Ghana international Kevin-Prince Boateng had been training alone during pre-season after parting ways with Bayern Munich.
His time at the German champions was truly successful as he won several trophies including the Champions League on two occasions.
Boateng, 32, won the Bundesliga title nine times and is also a World Cup winner with the German national team.
His experience will be helpful to Lyon who aims to challenge the star-studded PSG team for the French crown this season.
Source: Ghanasoccernet