Introduction: Family planning and birth control are the main goals of governments worldwide for population growth control and appropriate contraceptive use is a measure to reach these goals. Investing in health education for better contraceptive use and more reasonable allocation of existing resources are of great help in materializing the goals. Steps to Behavior Change (SBC) can be a good model to develop and evaluate family-planning programs. The aim of this study was to investigate the influence of family-planning education through modified SBC model on the reduction of unwanted pregnancies in oral contraceptive (OC) users. Materials & Methods: This clinical trial study was carried out at Mashad Urban Health Centers. Data gathering was done through interviews and completion of a researcher-devised questionnaire for 290 randomly chosen women from the aforementioned centers. The subjects were randomly divided into two case and control groups. The intervention was done based on modified SBC model and post-tests were given three and six months after the introduction of the model.Results: There were no significant differences between the two groups prior to the intervention, but significant differences in the mean values of knowledge, approval, intention, practice and advocacy were seen in the experimental group compared to the controls (p<0.001). Additionally, significant reduction in oral contraceptive side-effects and unwanted pregnancies were seen in the experimental group following the intervention. Conclusion: Following the success of modified SBC model in this study, it is suggested that attempts be made to improve the individuals’ self-efficacy to more competently use the provided health services. Developing self-efficacy in these subjects for better contraceptive use, can be effective in decreasing the cost related to unwanted pregnancies and misuse of contraceptive methods especially OCPs.