This case report highlights a novel approach to strengthening the repair of a split peroneus brevis tendon tear with a peroneus quartus muscle autograft. We describe a 51-year-old woman with a longitudinal split tear of the peroneus brevis tendon confirmed by magnetic resonance imaging. Intraoperatively, a peroneus quartus muscle was appreciated, resected, and used as an autograft in the repair of the peroneus brevis tendon. Use of a peroneus quartus muscle as an autograft in peroneal tendon repair has not been documented in the literature, to our knowledge.