Lewandowski will sign a four-year contract with a release clause set at 500 million euros ($511.35 million dollars), Barcelona said in a statement.
Lewandowski, who had 12 months remaining on his Bayern contract, moved to Barcelona for 45 million euros with five million euros in add-ons, the 26-times Spanish champions confirmed.
The 33-year-old has joined the team on their U.S. pre-season tour where he completed his medical.
Lewandowski scored 344 goals for Bayern in 375 appearances, winning the league title every year and the Champions League in 2020.