The authors retrospectively reviewed 24 patients who underwent posterior calcaneal displacement osteotomy (PCDO) for posterior tibial tendon dysfunction and adult acquired flatfoot deformity from 1991 to 1996. The average follow-up was 27 months. Analysis consisted of preoperative and postoperative evaluation of radiographs, as well as postoperative subjective results. Ancillary procedures included flexor digitorum longus tendon transfer (n = 19), tendo Achilles lengthening (n = 21), tibialis anterior tendon transfer (n = 5), naviculocuneiform joint arthrodesis (n = 4), and first metatarsocunieform joint arthrodesis (n = 1). The talo-first metatarsal angle on the lateral view decreased from a preoperative average of 22.13 degrees to a postoperative average of 8.50 degrees. The talo-first metatarsal angle on the anteroposterior view decreased from an average preoperative value of 22.96 degrees to a postoperative average of 11.04 degrees. In all cases, talar head coverage at the talonavicular joint improved. Subjective results were categorized as good (n = 17), satisfactory (n = 5), and poor (n = 2). Complications included sural neuritis (n = 6), Achilles tendon rupture (n = 2), difficulty with fixation (n = 2), and undercorrection of deformity (n = 2). Patients who had higher preoperative and postoperative talo-first metatarsal angles on either the anteroposterior or lateral radiographs had significantly poorer outcomes (p = .0403, p = .002, p = .009, p = .001, respectively). In addition, those patients who had medial column fusions had statistically significant poorer subjective results (p = .015). Patients who had flexor digitorum longus (FDL) tendon transfers did significantly better than those patients who did not have FDL transfer (p = .004). The authors conclude that the posterior calcaneal displacement osteotomy is a reasonable option for management of posterior tibial tendon dysfunction in the adult acquired flatfoot.