The 27-year-old joins Thomas Tuchel’s men for preparations ahead of next season with the hopes of getting his chance with the Blues in the upcoming season.
Rahman excelled on loan at Greek side POAK Thessaloniki in the second half of last season, helping the club win the FA Cup.
The former Augsburg player has struggled since joining the London club in 2015 but looks set to challenge for a position under German manager Thomas Tuchel.
Chelsea started preparations for the upcoming season last week but had more of their players arriving on Monday, including Baba Rahman.
The UEFA Champions League winners have lined up a series of friendlies ahead of their Super League clash against Villareal next month before the season starts.