This study reviewed retrospectively preoperative magnetic resonance imaging (MRI) and intraoperative findings of 32 patients who underwent surgical treatment of longstanding peroneus brevis tendon pathology. The purpose of this study was 3-fold: 1) to determine the sensitivity and specificity of MRI diagnosis of peroneus brevis tendon tears as confirmed by surgical findings, 2) to define the prevalence of osseous and soft-tissue pathologies that coexist with peroneus brevis injuries, and 3) to compare the occurrence rates of other associated pathologies found on MRI to that of the surgical findings. MRI diagnosis of a peroneus brevis tendon tear showed 83% sensitivity and 75% specificity to intraoperative findings. Four false positive and 2 false negative cases were identified. Coexisting conditions identified by MRI included a low-lying muscle belly/peroneus quartus (44%), anterior talofibular ligament rupture (50%), flattened/hypertrophy peroneus longus tendon (56%), increased signal intensity within peroneus longus tendon (53%), and a flat/convex fibular groove (78%). These results show that peroneus brevis tears rarely present as isolated injuries and support the need for a comprehensive preoperative clinical evaluation and MRI assessment of the entire lateral ankle complex.