We present a case of a postpartum female with iliopsoas fasciitis in the puerperium. Two days after a spontaneous vaginal delivery at 38 weeks without any complications, the patient complained of pain in the left thigh and hip, associated with a temperature of 38 degrees C. Consequently, she could not walk 4 days after delivery and her body temperature had increased to 39 degrees C. Extreme left flank pain and tenderness in the left pelvic wall were prominent, whereas the tenderness in the pelvis was moderate. Magnetic resonance imaging led us to diagnose iliopsoas fasciitis. This was complicated by sepsis but improved after a protracted antibiotic treatment without any surgical intervention. A literature review revealed that serious complications, including sepsis or permanent functional disturbance, could arise although retroperitoneal fasciitis and/or abscesses are very rare after vaginal delivery. Iliopsoas fasciitis could be considered when patients complain of extreme pain in the pelvic wall, sacroiliac joint region, or thigh-symptoms that are uncommon in uncomplicated endometritis.