This article explores the role of within-person fluctuations in employees’ daily surface acting and subsequent personal energy resources in the performance of organizational citizenship behaviors directed toward other individuals in the workplace (OCBI). Drawing on ego depletion theory (Muraven & Baumeister, 2000), we develop a resource-based model in which surface acting is negatively associated with daily OCBIs through the depletion of resources manifested in end-of-day exhaustion. Further integrating ego depletion theory, we consider the role of employees’ baseline personal resource pool, as indicated by chronic exhaustion, as a critical between-person moderator of these within-person relationships. Using an experience-sampling methodology to test this model, we found that surface acting was indirectly related to coworker ratings of OCBI through the experience of exhaustion. We further found that chronic levels of exhaustion exacerbated the influence of surface acting on employees’ end-of-day exhaustion. These findings demonstrate the importance of employees’ regulatory resource pool for combating depletion and maintaining important work behaviors. Implications for theory and practice are discussed.