["Psychology &Marketing, EarlyView. ", "\nABSTRACT\nAmid rising loneliness and declining community participation, service environments have become increasingly important sites of everyday social interaction. Existing research has largely treated Third Place as a property of a space, leaving unexplored how individual customers come to perceive a servicescape as a social home. This study extends Third Place theory by examining Third Place perception as a cumulative subjective sense that a setting functions this way. Drawing on social exchange theory, we propose that reciprocal social exchange, the simultaneous giving and receiving of social‐emotional resources, is the within‐person mechanism through which this perception develops. Using a four‐wave longitudinal survey of 404 regular patrons of British pubs and a Bayesian random‐intercept cross‐lagged panel model, the study demonstrates that social connection and prosocial behavior are reciprocally related within‐person. Elevations in reciprocal exchange predict higher Third Place perception at the study's endpoint. These findings extend Third Place theory from a descriptive account of what relational settings look like toward a process account of how customers come to perceive them that way. These findings suggest that the social value of service environments may depend not simply on providing welcoming environments for passive co‐presence, but on creating conditions that support reciprocal exchange.\n"]