BACKGROUND: Reconstruction of the complex upper extremity defects is a challenging procedure for reconstructive surgeons because of the complex anatomical and functional structure of this region. In reconstruction, local and regional flap options involving the composite tissues are restricted. The posterior interosseous flap (PIO) has been presented "in a single study" with a wide variety of uses, and in this study, the versatility of PIO has been tried to be emphasized by its multitude uses as well as its chance at adaptability to each case. Hence, due to this, the objective to highlight the versatile utility of the PIO flap in clinical practice and to present a good option for the reconstruction of complex upper limb defects for various cases have been targeted. METHODS: We used 26 PIO flaps in 25 patients (18 male and seven female patients) with upper limb defects. The main etiological causes were burn contracture, traffic accident, firearm and acute burn injury. Twenty-two flaps were harvested as fasciocutaneous and four flaps as osteo-fasciocutaneous manner, which were applied to the metacarpal defects. In this study, 25 flaps were transferred as pedicled flaps, of which 23 and 2 flaps had reverse and antegrade blood flows, respectively, whereas one flap was used as a free flap. RESULTS: The mean follow-up period was 14 months. All flaps except one, which had partial necrosis and secondary healed, survived completely. All patients were able to gain basic functions for daily routine activities in the late postoperative period. Patients and/ or their parents were satisfied with the postoperative functional and aesthetic improvements. CONCLUSION: Many advantages of the PIO flap make it useful for the reconstruction of upper limb complex defects. It can be versatilely used based on changing its flow direction and enrichment of contents.