Background and objective: Management of postoperative pain is one of the important concerns of medical team in order to promote trust, comfort and reduce pain. Hence this study was undertaken to assess the effectiveness of rhythmic breathing exercise on postoperative pain among patients undergone major abdominal surgery. Materials and methods: The study was a quantitative research approach and pre experimental (one group pre-test and post-test) design, was adopted. Thirty patients who had undergone major abdominal surgery were selected from MGMCRI at Puducherry by using purposive sampling technique. Results: The pre-test and post-test mean value of pain level was 7.83 with standard deviation of 0.95 and 5.70 with standard deviation 0.84, respectively. The obtained p value which was highly significant at p < 0.001. Conclusion: Hence the result showed that rhythmic breathing exercise was highly effective in reducing postoperative pain among patients undergone major abdominal surgery.