Twenty-nine consecutive patients who underwent diagnostic or therapeutic subtalar joint arthroscopy for sinus tarsi syndrome were retrospectively reviewed. The mean length of follow-up was 18 months. There was a history of trauma in 86% of the patients, with an inversion sprain being the most common predisposing injury (63%). All patients had a primary preoperative diagnosis of sinus tarsi syndrome. Magnetic resonance imaging was useful in identifying subtalar joint chronic synovitis and/or fibrosis in all 26 patients who were imaged. Subtalar joint synovectomy was the most common procedure performed. Twelve patients had 15 additional operative procedures. One patient required an arthrotomy secondary to arthrofibrosis. There were no postoperative complications. The mean return to full activity was 4 months. The mean postoperative AOFAS Ankle-Hindfoot Scale score was 85 points. Subtalar joint arthroscopy has proven to be a relatively safe and effective diagnostic and therapeutic technique in the management of sinus tarsi syndrome.