Building on recent literature that addresses how social workers use knowledge to make practice decisions, this ethnographic study of mental health workers in a residential treatment center for children asks what modes of agency workers enact and how they use formal training in Therapeutic Crisis Intervention (TCI) during crises. Based on 13 months of participant observation and 36 semistructured interviews, this study demonstrates that, while workers routinely employed specific intervention techniques taught in the TCI curriculum, they rarely reported using its step-by-step decision-making process. Instead, faced with an imperative to act, workers reported using a mode of agency characterized by what they term “instinct,” automaticity, physicality, and instantaneous mental simulation of possible outcomes. I discuss these findings in light of Pierre Bourdieu’s work on habitus, considering implications for crisis intervention training, prescriptive models of decision making, and the further development of contextually sensitive models of agency in social work practice.