Background and aim: Increasing of gap between the inter-recti abdominal muscles during pregnancy and postpartum, called diastasis recti, which is the result of weakness and transverse stretching of the linea alba. In this disorder, lumbopelvic control is impaired, which is one of the causes of lumbar pain and disability after childbirth. One of the treatment methods for this disorder is rehabilitation training in the core area of the trunk. This study aimed to evaluate the effect of isometric-isotonic exercises on improving the width of linea alba, lumbopelvic control, pain, and disability in women with diastasis recti after postpartum. Methods: This study is a randomized controlled double-blind clinical trial in which 24 women with diastasis recti were participated and divided into two groups of exercise and control (n=12) with a mean age of 29. 66 (4. 97) and 28. 25 (4. 55), respectively. We used the digital caliper for the assessment of diastasis recti and lateral step down test for assessment of lumbopelvic control. Also, vas scale and Oswestry questionnaire were used for assessing pain and disability. The exercise group exercised for 8 weeks and 3 sessions per week and the control group continued their normal life routine. Results: By comparing the mean results of the intervention and control groups after eight weeks of isometric-isotonic training, a significant difference was observed in the rate of rectus diastasis and lumbopelvic control, pain, and disability (p≤ 0. 05). Also, ETA squared of the effect size of exercise showed that these exercises had a very strong effect on the transverse distance of Lina Alba (0. 846), the degree of pelvic lumbar control (0. 850), the degree of disability (0. 720), but had a moderate effect on pain variable (0. 546). Conclusion: Isometric-isotonic exercises of core stability can improve lumbopelvic control by reducing the width of Linea Alba and thus reduce lumbopelvic pain and disability in people with diastasis recti. According to the results, the exercises presented in this study can be used to treat diastasis recti.