The objective of the paper is to determine the impact of corporate social responsibility (CSR) on financial performance and moderate role of enterprise size. Quantitative method is used in the study with research samples of 389 garment and textile enterprises in Vietnam. The results show that CSR has positive effects on financial performance on these enterprises. In addition, the firm sizes as a moderating role in this relationship, the bigger the business, the better the relationship between CSR and financial performance. However, for smaller businesses, this relationship opposite effect. The implementation of CSR reduces the financial performance. Research results show that CSR has a positive impact on financial performance, then creates motivation for enterprises to implement CSR voluntarily. However, small businesses should have a long-term strategic plan to implement CSR part by part in order to ensure the survival of the business