PurposeThe ability of construction firms to become more environmentally conscious and socially responsible for their business activities has been touted as the key driver for improved individual firms' competitiveness. This study explores the key dimensions of corporate social responsibility (CSR) practices and their impact factors among construction firms.Design/methodology/approachThrough the institutional, stakeholders and self-determination theories, this study proposed a conceptual framework of CSR implementation. For its validation, data were collected from 90 top-tier construction firms using an online survey and analyzed via a two-pronged factor analysis method.FindingsThe empirical results demonstrate that the CSR practices of construction firms include eight key dimensions, e.g. shareholders' interests, government commitment and CSR institutional arrangement. The three key groups of impact factor of CSR implementation are (1) identified factors (i.e. contractors' perceived importance of CSR practices); (2) external institutional factors (i.e. coercive and normative factors and mimetic factors); and (3) intrinsic factors (i.e. strategic business direction, resource and capability and organizational culture).Practical implicationsThe research findings inform the practitioners about how to enact, manage and improve firms' socially responsible goals so as to fulfill their key stakeholders' requirements and expectations and thus enhance their legitimacy in construction businesses.Originality/valueThis study contributes to CSR knowledge by identifying and empirically demonstrating valid measurements of the key dimensions of practices and impact factors toward CSR implementation by construction firms.