To evaluate the efficacy of the third-generation bisphosphonate in Egyptian patients with OI and determine the molecular genetic analysis of some cases. The study was prospectively conducted for >1.5 years between December 2017 and April 2019. This study enrolled 70 cases with OI (age range, between 2 months - 15 years). Through history taking and clinical evaluation were done. Moreover, all patients received zoledronic acid every 3–6 months based on age. Patients were assessed using dual-energy X-ray absorptiometry and plain X-ray before and after therapy. Gene sequencing analysis was performed in only 15 cases. The patients were followed up at 1.5 years from therapy. 60% of patients included in the study were males. Fracture onset started at >5 years old in three patients, whereas 32 (45.7%) patients suffered from fracture since the neonatal period. All patients had lower limb deformity, whereas 15 (21.1%) and 19 (27.1%) patients had upper limb deformity and scoliosis respectively. A significant improvement in Z-score was noted during follow-up, and 67 (95.7%) patients had improved. Appendix 1 shows the genetic analysis of selected cases. Third-generation bisphosphonates showed better results in patients with OI. However, future large-scale studies are warranted to confirm these results. Also, genetic analysis is necessary for the development of the much-needed targeted therapies to improve the outcome in affected individuals.