This chapter examines how developed countries’ multinational companies interplay perceptively between corporate social responsibility (CSR) and sustainability in developing transitional economies. The chapter presents findings from a study on CSR perceptions of MNC subsidiaries in Vietnam. The study draws on the theories of CSR pyramid and triple pillars of sustainability and employs a multi-case study design. CSR perceptions of seven well-established MNC subsidiaries in Vietnam were examined. The findings indicate that CSR perceptions covered four dimensions of the pyramid framework—economic, legal, ethical, and philanthropic—as well as sustainability-oriented responsibilities. It is notable that the four dimensions of the CSR pyramid were presented in a specific manner with an overarching responsibility toward sustainability. Therefore, it is implied that CSR should be understood from a broad perspective that includes sustainability. The three pillars of sustainability—economic, social, and environmental—are an umbrella covering the business’s economic, legal, ethical, and philanthropic responsibilities. In addition, sustainability-oriented responsibility is an overarching responsibility toward both the company’s and the community’s sustainability. From the research findings, we propose a modified CSR pyramid with a new overarching dimension of sustainability responsibility. The research also adds to a growing body of literature on CSR-sustainability of MNC operating in developing countries. With the proven link between the managers’ perceptions and the organization commitments and practices, it could be said that the grounds are there for actions toward the sustainability goal to take place.