Purpose The purpose of the study is to investigate the effect of trunk stabilization exercises accompanied by deep neck flexor strengthening exercises on sitting balance and head alignment of children with spastic diplegia. Methods Ten children diagnosed with spastic diplegia were randomized. The experimental group (n=5) underwent trunk stabilization exercise paired with deep neck flexor strengthening exercise, and the control group (n=5) underwent only trunk stabilization exercise. The interventions were designed to last 30 minutes a session, and a total of 18 sessions were performed over a period of six weeks. Evaluations were performed twice before and 6weeks after the intervention. The trunk control measurement scale (TCMS), craniovertebral angle were used to compare the effects of exercise methods. Results There was a statistically significant difference due to an increase in the mean value in the sitting posture balance and alignment between the experimental and control group (p<0.05). Conclusion Trunk stabilization exercise accompanied by deep neck flexor strengthening exercise may be an effective intervention for enhancing sitting posture balance and alignment, upper extremities function of children with spastic diplegia and thus should be utilized more in clinical practice.