BACKGROUND: Considering the key role of health volunteers in promoting community's health, their effective training is of particular importance. Training can be more effective through cooperative and learner-centered methods. Role-play is among the cooperative methods with numerous advantages. Considering the positive impact of training via various methods, we aimed to compare training through role-play and lecture on health volunteers' health knowledge in selected comprehensive health centers of Shiraz, Iran. METHODS: This quasi-experimental study was conducted on all health volunteers in four comprehensive health centers selected via random cluster sampling during the second half of 2017. The participants were divided into intervention and control groups and took part in the pretest based on the book entitled "Promotion of Breastfeeding". Based on the pretest results, health volunteers trained the participants in three educational sessions. The two groups were evaluated again immediately and two months after the intervention. RESULTS: The mean age of the participants was 49.97 ±â€¯8.1 and 46.52 ±â€¯10.74 years in intervention and control groups, respectively. Most participants were married (94.8%) and had diplomas (92.1%).A significant difference was seen between both groups in knowledge scores at the three time points (P < 0.001). A significant difference was found between the two groups regarding knowledge scores immediately and two months after the intervention (P < 0.001), indicating the effectiveness of training through role-play. CONCLUSION: The advantages of role-play, including development of communication skills and active listening, resulted in the learners' enthusiasm and motivation. This method was accompanied with higher educational output as well as longer knowledge persistence. Role-play increased cooperation and group discussions performed after the role-play promoted the transfer emotional experiences.