We propose three interlinked ways that theory helps researchers build causal claims from ethnographic research. First, theory guides the casing and re-casing of a topic of study. Second, theoretical work helps craft a clear causal question via the construction of a contrast space of the topic of investigation. Third, the researcher uses theory to identify social mechanisms that condense causal accounts. We show how each step can accommodate the everyday meanings typically central to ethnographic research's contributions. This tripartite role for theory thus preserves ethnography's traditionally recognized strength in interpretive validity, while realizing ethnography's potential for offering causal, and partly generalizable, accounts that can engage the wider sociological discipline. The discussion brings ethnographic research into conversation with recent debates on the role of mechanisms, comparative and counterfactual thinking in causal accounts. We illustrate and defend our argument for theory in ethnography with an extensive analysis of a contemporary ethnographic monograph along with briefer attention to parallel uses of theory in two other ethnographic studies.