<p>Brands are increasingly leveraging firm-generated content (FGC) on social media platforms to launch new products and communicate their brand personality and culture. Our study focuses on how mentions strategy affects user engagement in brand-based social media. We propose a theoretical framework to shape the relationship between mentions embedded in FGC and user engagement, leveraging attention theory and cognitive load theory. We further develop an econometric model to empirically examine the role of mentions strategy in user engagement. Our findings indicate that the mentions strategy strengthens low-level user engagement (likes) but weakens high-level user engagement (comments). More importantly, we find heterogeneous effects of mentions strategy on user engagement between informative content and brand-personality content, showing that the negative effect of mentions on high-level user engagement is stronger for informative content than brand-personality content. In addition, we examine the heterogeneous effect of the mentioned accounts on user engagement, revealing that the positive impact of mentioning more influential accounts on low-level user engagement is significantly greater for informative content than brand-personality content. This study contributes to the information systems literature by offering a deeper understanding of how mentions strategies function within brand communication on social media. It also provides practical guidance for brand managers seeking to optimize their FGC strategies to foster greater user engagement.</p>