The present study aimed to identify the determinants of social distancing behavior in the context of COVID-19 through the application of an integrated social cognition model. The integrated model was based on the theory of planned behavior [13] augmented to include additional predictors relating to normative (moral norm), anticipated affect (anticipated regret), volitional (action planning), and nonconscious (habit) determinants of health behavior. The model was tested in data from a correlational prospective survey study in two samples of Australian and U.S. residents subject to national or local “shelter-in-place” orders. Results indicated that intention and habit were significant predictors of social distancing behavior in both samples. Subjective norm, moral norm, and PBC were significant predictors of social distancing intention. In addition, intention-mediated effects of these social cognition constructs on social distancing behavior in the U.S. sample, but did so only for moral norm in the Australian sample. Action planning did not mediate effects of intention on behavior in either samples but moderated the intention–behavior relationship in the Australia sample. Inclusion of past behavior attenuated effects of social cognition constructs in the models in both samples, although habit and intention remained significant determinants of social distancing behavior in both samples. Excluding participants in the U.S. sample not subject to formal “shelter-in-place” orders, or had the orders lifted during the study, did not affect the pattern or size of the effects in the model, providing evidence that formal orders did not have a substantive bearing on the determinants of social distancing behavior in this sample.