Partnering with social media influencers (SMIs) in corporate social responsibility (CSR) initiatives has become increasingly popular, but their role in conveying CSR initiatives remains unclear. Grounded in legitimacy theory and Max Weber’s concept of charismatic legitimation, this research investigates how SMIs’ leadership in opinion and taste impacts the normative and pragmatic legitimacy of CSR initiatives. An online survey of 491 U.S. influencer followers shows that perceived SMI opinion leadership enhances CSR normative legitimacy, which in turn increases stakeholders’ willingness to support. Our findings contribute to public relations and CSR research by highlighting the importance of CSR legitimacy, introducing charismatic legitimation to explain SMIs’ roles, and distinguishing between opinion and taste leadership. These insights help companies choose SMIs who enhance CSR legitimacy and support.