Why are some people more successful than others at fitting in culturally over time? Prior research has offered divergent and seemingly inconsistent answers to this question. One perspective has highlighted the importance of shared values in shaping behavior, while another has emphasized the role of situational cues and the ability to read the group’s cultural code. We develop a theoretical account that reconciles these competing perspectives. Drawing on dual-process theories of culture and cognition and the distinction between constrained and unconstrained situations, we develop a situated theory of cultural fit. We argue that values matter for behavior in unconstrained situations—in particular, for the choice to remain at or voluntarily exit from the organization. In contrast, perceptual accuracy matters for behavior in constrained situations—specifically, for the capacity to exhibit real-time linguistic conformity with peers. We further show that a person’s behavior and perceptual accuracy are both influenced by observations of others’ behavior, whereas value congruence is less susceptible to peer influence. Drawing on email and survey data from a mid-sized technology firm, we use the tools of computational linguistics and machine learning to develop longitudinal measures of cognitive and behavioral cultural fit. We also take advantage of a reorganization that produced quasi-exogenous shifts in employees’ interlocutors to identify the causal impact of peer influence. We discuss implications of these findings for research on person-culture fit, cultural change and transmission, dual-process models of culture and cognition, and the pairing of surveys with digital trace data.