Objectives: The purpose of this study was to evaluate the effects of assertiveness training on assertiveness behavior, problem solving ability, and interpersonal relationships of nursing college students. Methods: A nonequivalent pre- and post-test experimental design was used. This study included 15 subjects in the experimental group, and 15 subjects in the control group, who were sophomore nursing students recruited from Gachon Nursing School located in Inchon City. The experimental group received 8 series of a ready planned and reorganized assertiveness training course, while the control group did not receive any training. The 120 minute training session was held on a weekly basis. The Maan-Whitney U Test was done to identify the changes in scores of assertiveness behavior, problem solving ability, and interpersonal relationships between the experimental and the control groups, after the assertiveness training. The data were collected before and after each part of the assertiveness training. The data collection period was from May 7 to July 10, 2001. Results: 1) The assertiveness behavior scores of the nursing students who participated in the assertiveness training were higher than those of the nursing students who did not participate in the assertiveness training. 2) The self problem solving evaluation scores of the nursing students who received assertiveness training were higher than those of the nursing students who did not receive the training. 3) The interpersonal relationship scores of the nursing students who participated in the assertiveness training were higher than those of the nursing students who did not participate in the assertiveness training. Conclusion: The study results showed that the assertiveness training was effective in promoting assertiveness behavior, problem solving ability, and changes in interpersonal relationships in nursing college students. It is suggested that well designed strategies are needed in the further studies in order to expand and apply the assertiveness training to other nursing student and nurse cohorts.