The Evans calcaneal lengthening osteotomy has gained popularity in recent years for the treatment of symptomatic flexible pes planus deformity. To our knowledge, the occurrence of a stress fracture of the fifth metatarsal has not been reported after this procedure. We report two such cases and discuss the probable mechanism of this problem, a relative overloading of the lateral aspect of the foot. Both cases were treated successfully with immobilization. Clinicians should be aware of this possible problem and treat it appropriately.