The first extensor compartment of the wrist is a distinctly variable anatomical area. Anatomical variations in this region contribute to the pathophysiology and treatment failure of de Quervain’s disease, which is a kind of tenosynovitis that develops in the first extensor compartment of the wrist. We aim to describe the first extensor compartment morphology, to evaluate the septum frequency, location of the septum, and the number of tendons of abductor pollicis longus (APL) and extensor pollicis brevis muscles (EPB). First extensor compartment of 87 wrists of 45 cadavers were dissected. The presence or absence of septum and number of tendon slips of APL and EPB revealed. The proximal and distal widths of the compartments were measured. Septums were detected in 60.9% (n=53) of the wrists. Incomplete (distal) and complete (proximal) septa were present in 35.6% (n=31) and 25.3% (n=22) of the cases. Only 26.4% of the wrists had a single slip of APL tendon. The Remaining had multiple slips. The median inner width of the proximal and distal compartments in all wrists were calculated as in the order of 9.11±1.14 mm and 8.55±1.12 mm. We believe that understanding the anatomy of the first extensor compartment in the Turkish population would be helpful to surgeons, radiologists, and physiotherapists to diagnose and manage de Quervain’s disease.