Environmental, social, and governance (ESG) disclosure has become a critical component of corporate reporting. However, the effectiveness of this type of disclosure remains poorly explored among small and medium enterprises (SMEs), despite the fact that these businesses represent the majority of firms around the world. By leveraging on a dataset of Italian listed SMEs, we fill this gap to shed new light on the effects of nonfinancial disclosure on the cost of capital. The study reveals that, in stark contrast with the evidence on large companies, environmental disclosure for SMEs is bound to provoke an increase in the cost of capital. Yet this pattern is capsized when the company is a family SME, as it benefits from environmental disclosure, as large companies do.