Background & Objective: Development of gross motor function in children with cerebral palsy has been a primary goal of physical therapists for decades. Suit therapy has been proposed as an adjunct to conventional physiotherapy to treat the impairments associated with cerebral palsy. Providing an orthosis along with the conventional therapy improves the motor performance of the child. Hence, this study aimed to determine the effect of modified suit therapy in gross motor function of spastic diplegic children. Method: A simple random sample of 30 spastic diplegic subjects in age group of 4-12 years fulfilling inclusion criteria from Mobility India, Bangalore was included. The outcome was evaluated using Gross Motor Function Measure-88 scale before and after the intervention. Suit therapy along with the conventional therapy is given for 2hrs daily for duration of 3 weeks. Results & Conclusion: Wilcoxon signed rank test and Mann-Whitney U test were used to find the significance of improvement before and after the intervention. There was statistically significant difference between the experimental and control groups (P=0.030). It is concluded that modified suit therapy along with conventional physiotherapy is effective in improving the gross motor function of children with spastic diplegic cerebral palsy.