This study aimed to examine the effects of a sexual education program (SEP) focused on sexual media literacy (SML) for school nurses. A quasi-experimental, pre-/posttest design was used to examine SML knowledge, awareness, reinterpretation skill, and self-efficacy. A total of 66 school nurses participated. The experimental group (n = 35) participated in an 18-hr SEP that focused on SML, while the control group (n = 31) did not. The experimental group showed significant improvement in knowledge (t = 6.47, d = 1.62, p < 0.001), awareness (t = 5.08, d = 1.19, p < 0.001), reinterpretation skill (t = 4.81, d = 2.28, p < 0.001), and self-efficacy (t = 8.29, d = 1.38, p < 0.001) as compared to the control group. The SEP developed in this study may be an effective educational intervention for school nurses.