Traumatic iliacus muscle injury is rare; it is usually caused by trauma or intense exercise involving the pelvic girdle; it can produce a hematoma with femoral nerve neuropathy. Spontaneous muscle hematomas occur in patients with coagulation disorders.A 45-year-old male with 18 days of evolution, with an intense pain in the right buttock, groin and iliac fossa, with an inability for hip flexion and ambulation caused by inadequate exercise (supine double leg lifts). On the physical examination: intense pain with bending and/or internal rotation of the right hip, positive Thomas maneuver, quadriceps rated 3/5; area of paresthesia in the right femoral nerve territory. Pelvic magnetic resonance imaging showed: right iliacus muscle tear with blood between its fibers. Initial treatment was rest and analgesics for eight days and gradual extension of the hip, axillary crutches with partial weight bearing and diathermy on the right abdominal lower quadrant, active hip exercises, bicycle and right quadriceps strengthening. The evolution was satisfactory, with full recovery in six weeks.