PURPOSE: The purpose of this study was to evaluate effects of a maternal sexuality education program for mothers of preschoolers. METHODS: A quasi-experimental with non-equivalent control group pretest-posttest design was conducted. The participants were 55 mothers of preschoolers in G city (Experimental group=27, Control group=28). The experimental group received the maternal sexuality education, and the control group received the program after the experiment. Data were collected during October and November 2012 through self-administered questionnaires at two times: prior to the intervention and after the intervention. Data were analyzed using chi2-test, Fisher's exact test and t-test. RESULTS: After the intervention, mothers in the experimental group reported significant differences in knowledge of sex (t=3.74, p<.001), attitude toward sex (t=4.31, p<.001), parent-efficacy on child sexuality education (t=11.96, p<.001). compared to mothers in the control group. CONCLUSION: These results indicate that a sexuality education program for mothers of preschoolers is effective in improving knowledge of sex, attitude toward sex, and parent-efficacy on child sexuality education. Therefore further study should be done with larger and varied participants to confirm the effects of sexuality education programs for mothers of preschoolers.