Sustainability encompasses three dimensions, i.e., economic, environmental, and social, which are commonly termed as Triple Bottom Line. Since most businesses are profit-oriented, economic sustainability is identified as the widely considered dimension of sustainability in prior literature. The present study investigates to what extent manufacturing companies are using social practices and assesses sustainability performance referring to social sustainability practices followed by manufacturing companies. To address this issue via a quantitative approach, data were collected using a questionnaire survey from 88 apparel manufacturing companies in Sri Lanka, and a PLS structural equation modeling was used to analyze the data. Findings indicate that both internal and external social sustainability practices positively impact all sustainable performance, i.e., economic, environmental, and social.