This move marks Benda's latest stint in the Championship, following previous spells with Swansea City and Peterborough United.
Millwall's Director of Football, Steve Gallen, is pleased with the signing, citing the need for competition in goal.
Gallen stated that Benda was one of several options considered to provide competition for Max Crocombe and George Evans.
The signing is expected to bring a high level of expertise to the Millwall goalkeeping department.
