Background: the humerus is the most mobile long bone of the upper limb. Humeral shaft fractures comprise about 3 to 5% of all body fractures. Objective: the aim of the work was to assess the results of using the flexible intramedullary nails in the treatment of humeral shaft fractures. Patients and Methods: the study included 20 patients presented to Alexandria Police Hospital and El-Zahra Hospital, suffering from humeral shaft fracture. A full workup including history taking, clinical examination and radiological evaluation as well as laboratory investigations was performed for every patient on admission. Results: the results obtained after a mean follow up time of 32 weeks, were excellent in twelve patients (60%), good in six patients (30%), fair in one patient (5%), and poor in another one patient (5%). The difference between excellent and good groups was statistically significant, that the younger the patient the more rapid the fracture healing occurred. Conclusion: flexible intramedullary nailing is a simple, easy semi rigid and quick technique for stabilization of humeral diaphyseal fractures in selected cases of humeral shaft fractures in different ages.