The purpose of this study was to investigate effects of Assertion Training of Humanistic Psychological Approach (AT-HPA) which emphasizes beliefs and attitudes concerning assertion rather than behavioral skills. Eleven middle aged women participated in AT-HPA program, which consisted of theory course and exercise course, for 10 weeks. They answered Assertion Inventory (AI) and Assertive Mind Scale (AMS) 5 times:pretest, middle test, post test, follow-up 1 month test and follow-up 3 months test. AI assessed behavioral skills of assertion and AMS assesses beliefs and attitudes of it. There was no significant change on AI in multiple comparison tests. On the other hand, there was significant increase on AMS from pretest up to post test and this effect maintained until follow-up 1 month test. Standard deviation of AMS was smaller than that of AI. This result implied that effects of AT-HPA on beliefs and attitudes were more stable than on behavioral skills. It was concluded that AT-HPA effects on beliefs and attitudes rather than on behavioral skill.