How economic crises impact the boundaries of firms has been offered virtually no attention in the literature on the theory of the firm. I review the best-known theories of the firm and identify the variables that matter for the explanation of firm boundaries. I then examine how an economic crisis may impact these variables and change efficient firm boundaries. The various theories of the firm have difficulties explaining how firms efficiently adapt their boundaries to such prominent characteristics of economic crisis as declining demand and increased costs of external finance. However, all these theories stress uncertainty as an antecedent of firm organization, and as uncertainty is also an important characteristic of an economic crisis I examine how uncertainty is allowed to play out in the various theories in order to identify what predictions we can derive from the theory regarding changes in efficient firm boundaries as consequence of changes in uncertainty. The analysis suggests that we need to be more precise in describing the nature of the uncertainty that is assumed in the various theories. Moreover, allowing for changes in levels of uncertainty requires that we take the processes of boundary changes into account in the theory of firm boundaries.