A growing body of research is exploring corporate communication in relation to corporate social responsibility (CSR) activities on social media (SM). Nonetheless, while these studies have shown that SM communication may be an effective tool for reaching and engaging various stakeholders, how the design of corporate CSR communication engenders trustworthiness has yet to be examined. To address this gap, we suggest that SM communication may include important signals related to trust; thus, we investigate whether companies use sources of trustworthiness (reputation, (...) performance, and appearance) while communicating with stakeholders and the response of the latter to such communication. Our empirical analysis is based on a database containing over 66,000 CSR-related messages from eight companies focusing on communication extracted from Twitter. These data are coded according to three sources of trustworthiness and two dimensions of CSR communication (social and environmental). Our findings indicate that all three attributes of trustworthiness are used by companies in their CSR social media communication. We also document how corporate efforts to use CSR communication that engenders trustworthiness influence stakeholder engagement. Our study therefore contributes to the literature on trust in relation to CSR by illustrating the importance of signaling that includes different sources of trustworthiness or their combination in corporate communication. By analyzing how the various trust attributes included in CSR communication affect SM reactions, we also identify which attributes lead to greater stakeholder engagement overall, particularly for the two analyzed dimensions of CSR communication. (shrink)