Introduction: Preterm infants are exposure of many painful procedures during care and treatment, and applying non-pharmacological methods helps in decreasing pain effects and providing them with comfort and health. Therefore, this study investigated the effect of massage on preterm infants' pain caused by invasive procedures in neonatal intensive care unit. Method: This study was a semi-experimental research conducted on 82 infants in the neonatal intensive care unit. The procedure of sampling was random and all infants have been allocated two groups including experimental and control. The pain score was assessed for both groups at the first session of conducting invasive procedure. Then, experimental group benefited from massage for 5 days while control groups just received routine care. After this period, the pain score was assessed before, during and after intervention. Descriptive and inferential statistics were employed to analyze NIPS questionnaire by using SPSS software. Results: No statistically significant difference was detected in pain scores obtained before, during and after procedure for both groups before the intervention. In addition, there was a statically significant difference in pain scores gained by two groups during implementing procedure. After procedure implementation, pain score for experimental and control group was 2.5±0.6 and 3.4±0.6, respectively. These values confirmed that the amount of pain during and after applying procedure was significantly different between the two groups. Conclusion: massage can be used as an effective solution since infants can feel and remember pain and frequent exposure to painful and constant circumstances results in physiological, mental, and behavioral complications.