Breast cancer is a common cancer among women, and early detection is important for breast cancer mortality and morbidity. The aim of this study was to determine the effects of daughters teaching their mothers about breast self-examination (BSE) and its health beliefs. In the study's first stage, 168 university students were trained by the School of Health students about BSE through group training methods. Then, these trained university students were asked to train their mothers about BSE. Data were collected before the training and then again after the training (1 month later). The study instruments included questionnaire forms and the Champion Health Belief Model Scale. The results were analyzed using paired- and unpaired-sample t test, analysis of variance, bivariate correlation analysis, and stepwise multiple regression analysis. The results show that women's knowledge level increased 2-fold after training, and the knowledge level difference between pretraining and post-training was significant (P = .000). The mothers' background information (hear-read) and BSE practice (P = .006 and .006, respectively) before the training process were found to be significant predictors of sociodemographic and other variables influencing the mothers' knowledge levels. The training increased the perceived benefit (P = .032) and confidence (P = .000) significantly. It was found that there was a negative but significant correlation between perceived barriers and BSE knowledge after the education (P = .019). It was found that mothers' knowledge level about BSE was higher after the education. Furthermore, perceived barriers decreased while other subscales increased. Education from daughter to mother can be used as a BSE training approach to increase women's knowledge about BSE.