The purpose of the research was to examine the effects of a teaching program in the workplace on factory employees’ health knowledge, beliefs and behavior regarding breast self-examinaion. Women who attended the one-session class were quasi-experimentally assigned to one of two groups. There were 142 women who went through these 3 stages: Pre-test, post test immediately after teaching class, and follow-up 3 months later. The teaching program improved knowledge, perceived benefit of breast self-examination, confidence in breast self-examination, and skill in the experimental group, and also reduced perceived barriers regarding breast self-examination. Also, during the 3 months of the teaching program, the percentage of those conducting periodic breast self-examination among the experimental group was greater than for the control group. According to this research, it will be much more efficient to make women conduct breast self-examination while enhancing the complete understanding of breast self-examination procedures and reducing the perceived barriers in the related teaching program.