This study empirically investigated the relationships among external factors (i.e., the imitation, compulsory and normative pressures, and governmental regulation), proactive environmental strategy, the adoption of green-supply chain management (GSCM) techniques, green corporation with suppliers, environmental performance, and organizational performance. To empirically demonstrate the relationships, 78 sample firms' data were collected from Korean manufacturing firms that are listed on the Korean stock market. The results of this study showed that a proactive environmental strategy mainly and positively influences the adoption of GSCM, and the introduction of a proactive environmental strategy is significantly and positively affected by governmental regulation. It was also found that governmental regulation has an indirect impact on the adoption of GSCM through the introduction of a proactive environmental strategy. Thus, it is asserted that governmental regulation, in Korean manufacturing firms, is the unique external factor on the adoption of a proactive environmental strategy, which facilitates the use of GSCM techniques. According to the results, it was observed that GSCM positively influences the levels of green corporation, and both GSCM and green corporation have positive effects on the improvement of environmental performance. Hence, it is suggested that the implementation of GSCM inevitably brings high degrees of green collaboration with suppliers. Finally, it was found that environmental performance has a significant and positive impact on the organizational performance of a firm. This result implies that high degrees of environmental performance, which bring both the efficient usage of materials and energy and the elimination of wastes, can lead to the increase of organizational performance.