In many service contexts, customers share the service setting with other customers. However, knowledge about the influences of fellow customers’ copresence remains largely fragmented. We address this deficiency by introducing the integrative concept of customer copresence influence modes (CCIMs) and investigate its potential consequences for service perceptions and evaluations. Following a grounded theory approach and drawing on in-depth, qualitative interviews with both managers and customers of a leading service company, we develop a typology of CCIMs, categorizing the various ways—interactions (reactive/proactive; social/instrumental), observations (information-seeking/comparative), and spillovers (spatial/behavioral)—in which fellow customers might influence the focal customer. Building on this typology we propose a conceptual framework with a set of testable propositions about consequences of CCIMs for the focal customer’s service experience and the service provider’s image. The CCIM typology and propositional inventory, in addition to offering directions for further research, emphasize the need for service managers to pay special attention to customer copresence because (1) its influence on service experience is contingent on a variety of factors, including some within the managers’ control, and (2) customers might assign responsibility to the service provider for both desirable and detrimental effects of customer copresence.