<p>The circular economy (CE) is essential to achieve sustainable economic growth. In an environment where government pressure demands sustainable business models, customers demand more environmentally friendly products, and economic uncertainty dominates some markets, companies are challenged to innovate away from linear business models. Despite this, the number of companies adopting circular business models remains limited. Therefore, using the Theory of Planned Behavior (TPB) and Entrepreneurial Orientation (EO) as theoretical antecedents, this research assesses the impact of both corporate social responsibility (CSR) and TPB mechanisms on the intention to adopt circular business models (ICBM) and examines how EO promotes ICBM through CSR in the context of small- and medium-sized enterprises (SMEs), in developed (Spain) and developing (Ecuador) economies. A survey was conducted, and 232 responses were collected from the selected firms. The hypothesized relationships were analyzed using partial least squares structural equation modeling (PLS-SEM). The findings reveal that company managers’ attitude and perceived behavioral control (PBC) significantly influence the ICBM, with PBC being the most influential factor. The results also confirm that internal (ICSR) and external (ECSR) corporate social responsibility positively influence the ICBM. Furthermore, the findings suggest that EO promotes ICBM through ICSR and ECSR, having more impact through ECSR. In turn, no significant differences between Spain and Ecuador were detected in the hypothesized relationships. This study not only contributes to the transition towards a CE and the implementation of the Sustainable Development Goals but also expands the existing knowledge base in the CSR, EO, and ICBM literature stream.</p>