Kirk M. Jackson was charged in March 2012 after one of his customers discovered a video camera under a tissue box cover.
Authorities then conducted an undercover operation at the office, and found 140 videos Jackson took of women in restroom stalls, tanning beds and massage therapy rooms.
Jackson was arrested and pleaded guilty in June to 14 counts of invasion of privacy, the St. Louis Post-Dispatch said.
Two women who had been videotaped spoke at the sentencing hearing about the emotional distress they experienced as a result of Jackson's actions, the Post-Dispatch reported.
Although Jackson's lawyer argued for a probationary sentence, a circuit judge handed down consecutive terms of four years on the first two counts.
Jackson received a suspended sentence on the remaining 12 counts, but if he violates probation, he could face an additional 48 years in prison, the Post-Dispatch said.