Background: It is necessary to apply a behavior-based safety (BBS) program to prevent at-risk behavior. An effective BBS program requires the implementation of not only behavioral definitions and a customized critical behavior checklist (CBC) but also observations of behavior, coupled with customized interventions at power plants. Method: In this study, a customized CBC and behavioral definition were developed through a review of five different sites that previously used a CBC. The rules of observation, flow, and target were established to initiate the observations. Customized interventions were selected to increase safe behaviors. CBC scoring was used to evaluate observed safe behaviors for three years. Recognized safe behaviors were evaluated with a questionnaire that included four items each for conformity and participation behaviors and were then analyzed through a factor analysis and a t-test. The questionnaires were conducted three months before and after the implementation of the BBS program. Results: The customized CBC, behavioral definition, and interventions were effective, such that observed safe behaviors and the levels of workers’ recognized safe behaviors increased. Conclusion: The application of the BBS program was found to increase the observed and recognized safe behaviors. Therefore, the program applied to this site can help increase safe behaviors at other identical or similar sites, as well as prevent an accident, which also corresponds with the results of prior studies.