Objective. The goal of this study was to assess the appropriateness of the theory of planned behavior in predicting health care waste segregation behaviors and to examine the factors that influence waste segregation behaviors. Methodology. One hundred and sixty-three health workers completed a self-administered questionnaire in a cross-sectional survey that examined the theory of planned behavior constructs (attitudes, subjective norms, perceived behavioral control, and intention) and external variables (sociodemographic factors, personal characteristics, organizational characteristics, professional characteristics, and moral obligation). Results. For their most recent client 21.5% of the health workers reported that they most definitely segregated health care waste while 5.5% did not segregate. All the theory of planned behavior constructs were significant predictors of health workers’ segregation behavior, but intention emerged as the strongest and most significant (r=0.524, P<0.001). The theory of planned behavior model explained 52.5% of the variance in health workers’ segregation behavior. When external variables were added, the new model explained 66.7% of the variance in behavior. Conclusion. Generally, health workers’ health care waste segregation behavior was high. The theory of planned behavior significantly predicted health workers’ health care waste segregation behaviors.