Objective: Nurses have an integral role in pain assessment and management. Adequate knowledge and positive attitudes toward pain management are essential to provide high-quality nursing care for cancer pain. The purposes of this study are to evaluate nurses' knowledge and attitude toward cancer-related pain and to assess the effectiveness of a pain management education program on nurses' knowledge and attitude toward pain. Methods: A quantitative, experimental design was used. Results: The total number of participants who were surveyed at three measurement points was 131, with a completion rate of 87.3%. Findings revealed that the score of knowledge and attitude toward cancer-related pain ranged from 14 to 35, with a mean of 23.6 (standard deviation [SD] = 4.38). The mean scores of the intervention group and the control group at two measurement points regarding knowledge and attitude toward cancer-related pain were 32.7 (SD = 2.8) and 32.8 (SD = 4.3) and 23 (SD = 5.5) and 22.2 (SD = 3.8), respectively. There were significant differences at three measurement points among the intervention group ( F = 114.3, P < 0.0005). There were no differences in the three measurement points among the control group ( F = 3.4, P = 0.055). Conclusions: Nurses have essential roles in cancer pain. A pain management education program can improve nurses' knowledge and attitude toward cancer-related pain.