The aims of this study are to investigate the inferior peroneal retinaculum (IPR) regarding morphometric parameters, and contents in the inferior peroneal tunnel (IPT). One hundred and nine embalmed cadaveric legs were dissected in prone position. The extension band of the IPR was found in 31.19% of cases. The mean of length, width at the origin, width at the middle part, width at the insertion, and thickness of the IPR [mm] were 23.42 ± 3.54 (17.05-33.68), 13.29 ± 2.56 (5.83-20.92), 14.50 ± 2.37 (6.68-21.34), 10.10 ± 2.63 (4.59-19.17) and 0.48 ± 0.16 (0.20-0.87), respectively. The angle of the IPR to the horizontal axis was 38.51 ± 7.07 (11.67-54.00) degrees. The IPT was divided into the upper and lower tunnels. The normal contents were the tendons of peroneus brevis and peroneus longus in the upper and lower tunnels, respectively. However, additional contents were found in the upper tunnel in 2 cases. One was the tendon of peroneus digiti quinti, and peroneus quartus in the other one. Moreover, an unusual accessory peroneal muscle coursed into the lower tunnel and inserted on the peroneal tubercle. Tears of the peroneus brevis tendon were observed in 2 cases. These morphometric data might be beneficial in surgical repair for IPR injury.