We experienced a patient in whom rupture of the peroneus longus tendon occurred after ostectomy of the peroneus tubercle of the calcaneus. Acute rupture of the peroneus tendon can be managed by end-to-end anastomosis, while neglected cases can be treated by tenodesis, tendon transfer, or tendon graft. In the current patient, the tendon ends were mildly retracted, yielding a small gap. We successfully repaired the retracted tendon ends after lengthening by Z-plasty.