INTRODUCTION: Understanding the contribution of the fibularis longus tendon to the support of the midfoot arches has potential therapeutic applications. This cadaveric study sought to quantify this support across both the transverse arch and medial longitudinal arch and to establish whether a correlation exists between this support and the angle at which the tendon enters the sole. MATERIALS AND METHODS: Markers placed in 11 dissected cadaveric foot specimens defined the arch boundaries. Incremental weights up to 150 N were applied to the fibularis longus tendon to simulate progressive muscle contraction, and associated changes in the transverse and medial longitudinal arch boundaries were recorded. RESULTS: A force of 150 N reduced the transverse arch distance by 4.6 (1.7) mm (mean [SD]) and medial longitudinal arch distance by 6.8 (1.4) mm. The angle of the fibularis longus tendon on the sole correlated well with changes in the transverse arch distance (slope ± s.e. = 0.56 ± 0.13 mm/degree, Pearson r = .83, p = .002) but only weakly with the medial longitudinal arch (0.18 ± 0.18 mm/degree, r = .32, p = .33). CONCLUSIONS: The results of this preliminary study raise the possibility that physical therapies targeting the fibularis longus tendon may be valuable in the management of midfoot arch collapse. The correlation observed with the transverse arch suggests the possibility that surgical modification of the angle of the fibularis longus tendon on the sole may benefit patients with transverse arch collapse.