Brands often seek endorsements by consumers on social media (e.g., likes on Facebook). But is this marketing strategy feasible for all brands? To answer this question, this research investigates in seven studies the processes that underlie consumers' intention to endorse brands on social media. We suggest that consumers aim to signal their identity by endorsing brands online. Based on the Brands as Intentional Agents Framework and related research in (social) cognition and consumer behavior, we argue that consumers on social media primarily want to emphasize their warmth rather than their competence. Experimental studies 1, 2, and 3 distinguish between nonprofit and for-profit brands and show that brand warmth (and not competence) mediates the effect of brand type (nonprofit vs. for-profit) on consumers' intentions to endorse brands and branded content on social media. Experiment 4 demonstrates that this process is moderated by brand symbolism (moderated mediation). A high level of brand symbolism increases the positive effect of warmth on consumers' intention to endorse brands online, but only for for-profit brands. The fifth experiment shows that these effects are conditional upon the public vs. private distinction in consumer behavior: consumers prefer to publicly affiliate with nonprofit (vs. for-profit) brands but with regard to private affiliations, there is no difference between both types of brands. In experiment 6, the causal role of warmth (vs. competence) is further examined. Finally, we demonstrate that perceptions of brands' warmth and not competence reduce the efforts that brands need to make to achieve consumers' endorsements on their real brand pages on Facebook.