Background: Postpartum blues are a common mental health problem during the early postpartum period. There are many alternative therapies to treat this. Tai Chi, which was initially created for self-defense, has developed into a graceful type of exercise that is now used to treat stress and several other health issues. Through its smooth, flowing movements, Tai Chi has been compared to meditation in motion. Therefore, the current study aimed to investigate the effectiveness of Tai Chi exercise on stress and postpartum blues among postnatal mothers. Study design: A quasi-experimental research design was used to fulfill this study using a pre-test and post-test one-group design. Methods: the study was applied in the Postpartum Unit at Mansoura University Hospital and home visit. Subject: the study included a convenient sampling technique of 100 postnatal mothers. Two tools were used: Tool I: Structured interview questionnaire and Tool II: Perceived Stress Scale-10 (PSS-10). Results: a statistically significant difference was found between stress mean scores and postpartum blues at (P=0.001) pre and post-Tai Chi exercise application. Also, a statistically significant difference in pre- and post-Tai Chi exercise application between the groups was reported in terms of postpartum blues levels. Conclusion: The Tai Chi exercise application has a significant reduction in mean post-test stress and postpartum blues scores among the studied postnatal mothers.  Recommendations: Applying a training program for pregnant women during the antenatal period about the importance of the Tai Chi exercise application to be able to use them as a part of routine care during the postpartum period.