Purpose: This study was intended to evaluate the effects of an Infant Health Promotion Program (IHPP) for mothers with their firstborn infants. Methods: This study employed a non-equivalent control group pretest-posttest design. The participants consisted of 17 mothers with their firstborn infants in the experimental group and 17 in the control group from two women’s hospitals. The experimental group received eight sessions of the program for four weeks. The collected data were analyzed using the chi-square test and repeated-measures ANOVA using an SPSS/WIN ver. 22.0. Results: The experimental group receiving the program had statistically significant higher levels of infant health promotion knowledge (F = 22.91, p < .001), social support (F = 27.64, p < .001), maternal role confidence (F = 8.25, p = .005) and health promotion behavior for infants (F = 16.85, p < .001) than the control group. The experimental group had a statistically significant lower level of parenting stress than the control group (F = 29.93, p < .001). Conclusion: The study’s findings indicate that the IHPP is effective in improving health promotion knowledge, social support, and maternal role confidence and decreasing parenting stress among mothers with their firstborn infants. A method of delivering intervention, focused on readily accessible online platforms, coupled with intervention
strategies grounded in the theory of self-efficacy, proves to be an advantageous approach for this particular target group.