Entrepreneurs on crowdfunding platforms increasingly rely on third-party certification. While prior studies on reward-based crowdfunding generally find that certification enhances performance, little is known about its role in prosocial crowdfunding, where backers are motivated by both financial returns and altruistic rewards. As a result, third-party certification may exert heterogeneous effects on these motivations, thereby influencing crowdfunding performance. This study integrates a theoretical model with empirical analysis to examine the mechanisms through which third-party certification affects prosocial crowdfunding performance. First, a theoretical model that incorporates backers’ financial and altruistic motivations is developed to analyze creators’ certification decisions and derive testable hypotheses. Then, these hypotheses are tested using data from Kiva, a lending-based prosocial crowdfunding platform. The results show that creators who adopt third-party certification generally achieve higher crowdfunding performance. Specifically, certification strengthens backers’ financial motivations while weakening their altruistic motivations. Financial motivations positively affect crowdfunding performance, whereas altruistic motivations have a negative effect. Moreover, creators are more likely to choose certification when their projects exhibit stronger financial (quality) signals and weaker altruistic signals.