To assess the occurrence of pelvic floor dysfunction (PFD) in pregnancy- related low back and pelvic pain (PLBP) patients, a cross-sectional study was performed, comprising 77 subjects. Each subject underwent physical assessment, and filled in the Urogenital Distress Inventory completed with gynaecological questions. Differences in the presence of PFD between PLBP patients and healthy controls as well as differences in pelvic floor muscle activity were tested for significance. Interaction by age and vaginal delivery were tested. PFD occurred in 52% of all PLBP patients, significantly more than in the healthy control group. In PLBP patients a significantly increased activity of the pelvic floor muscles could be demonstrated with respect to healthy controls. The occurrence of PFD and PLBP was influenced by a confounding effect of age. Clinicians should be aware of the relation between PLBP and PFD and hence address both problems at the same time.