Sako left Crystal Palace in the summer as a free agent, and following a brief period of training with West Bromwich Albion, the Mali international could feature for the midlands side against Preston North End next time out.
The 30 year old winger left Crystal Palace at the end of last season having scored six goals in 19 appearances in all competitions, as a fractured ankle in February brought his season to a premature end.
Due to the extensive list of players in front of him in the Palace pecking order; Andros Townsend, Jason Puncheon, and Wifried Zaga to name a few, Sako's trial with West Brom was sanctioned by manager Roy Hogson.
West Brom boss Darren Moore has been impressed with Sako's performances throughout the 10 day trial, and having also proven his fitness, Sako has earned a short-term deal with the 'Baggies'.