The state court in Augsburg found the 52-year-old guilty of sexually assaulting two women while they were asleep, and of filming sex with two girlfriends and a prostitute without their knowledge. He was further found to have been in possession of child pornography.
Förster had admitted to several of the crimes at the start of the trial and had agreed to pay compensation to his victims.
The prosecution wanted a jailed term of over four years, while the defence appealed for a sentences of no more than three years.
When Förster was arrested in December last year he was still a state parliamentarian for the SPD. But he gave up his seat in the Landtag and his membership of the party shortly after his arrest.