Adult-acquired flatfoot deformity is a progressive flattening of the arch of the foot that results from posterior tibial tendon insufficiency with a predilection for middle-aged women. A lateralized force vector associated with hindfoot valgus in adult-acquired flatfoot produces lateral ankle pain due to impingement at the lateral hindfoot, which can even lead to stress fractures of the distal fibula. Here, we present the rare case of a 73-year-old woman who presented with stress fractures of the bilateral taluses and unilateral distal fibula accompanied by severe adult-acquired flatfoot deformities.