Background: Diplegia is one of the most common types of CP in which lower limbs are affected more than upper limbs, Pelvic malalignment is common in growing patients with diplegic CP develops due to the combination of spasticity, muscle weakness, as well as incompetent muscle control, this can result in poor pelvic control and significantly limits the patient’s ability to maintain balance. Aim of the Study: This study was conducted to study the relationship between balance and pelvic alignment in diplegic cerebral palsy children. Materials and Methods: Fifty children with diplegic cerebral palsy from both sexes (18 girls and 32 boys) grade I (33) and grade II (17) according to gross motor function classification system and 1 (23), 1+(15) and 2 (12) according to modified Ashowrth scale. Their ages ranged from 7-10 years, postural deviations were evaluated using the 3D measurement system Formetric while balance was assessed using Biodex balance system. Results: There was a statistically significant relation between overall stability index (OASI) and pelvic alignment (pelvic tilt- pelvic inclination). Conclusion: The obtained results suggested that there was significant correlation between balance and pelvic alignment in diplegic cerebral palsy children.