Adherence to prescribed exercise is taken into consideration, especially when there are treatment-related obstacles. Aim: to evaluate effect of postoperative mastectomy exercise adherence on pain and wound healing. Research design: quasi-experimental research design. Setting: The research was dispensed in general surgical units and an outpatient clinic at Assiut University Hospital. Tools: four tools were used: Tool I: Interview structure questionnaire; designed by the researcher supported current national and international literature, and composed of two parts: Part (1): Patient demographics characteristics, Part (2): Patient's medical data. Tool II: Exercise adherent rating Scale, Tool III: (Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials) IMMPACT panel scale and Tool IV: Wound healing assessment scale. Results: Wound infections affected nearly half the control group (46.7%), slightly less than three quarters (73.3%) of the control group didn't complete postmastectomy activities. In terms of pain severity and pain interference with daily activities, there was a highly significant difference between the study and control groups P=<0.001**. Conclusion: adherence to post-mastectomy exercise improve wound healing and reduce pain level. Recommendations: Applying post-mastectomy exercise to a wider probability sample from various geographic areas to assist within the generalization of the findings.