The Evans osteotomy has become an important option in the surgical treatment of adult pes planus deformity of multiple causes. Despite its increasing popularity, however, no single study, to our knowledge, has thoroughly examined the structures at risk when performing the Evans osteotomy on the adult foot. We performed the Evans osteotomy on 20 adult cadaver specimens to determine which soft tissues and bony structures were endangered by the procedure. We found that the optimal Evans osteotomy site should be exactly 10 mm proximal to the calcaneocuboid joint because this location best affords the opportunity of avoiding damage to the anterior or middle subtalar facets in those specimens with separate facets. In addition, we determined that the sural nerve, peroneus longus tendon, and peroneus brevis tendon were consistently at risk during the operative approach. Regarding the medial soft tissues, we found that these structures did, in fact, consistently pass in the line of the Evans osteotomy, and so are at risk.