Complete paralysis of the anterior interosseous nerve was seen in 32-year-old army officer 5 weeks after he sustained a minimally displaced fracture of the proximal ulna. The fracture was immobilized in an arm cast. Thirteen weeks after injury, the cast was removed following evidence of bone union. Complete recovery of the flexor pollicis longus was noted 17 weeks after the injury, while recovery of the flexor profundus to the index finger to grade four lasted 10 months. To the best of our knowledge, this is the first case reported in the English language literature in which anterior interosseous nerve palsy follows isolated fracture of the proximal ulna.