Both responsibility beliefs and intolerance of uncertainty have been implicated in compulsive checking behavior. Despite this, the exact relationship of these two variableswith compulsive checking behavior is yet to be determined. Using a mixed sample of individuals consisting of compulsive checkers as well as non-clinical participants, we assessed the validity of a mediation model in which the relationship between responsibility beliefs and compulsive checking was mediated by intolerance of uncertainty. Although both responsibility beliefs and intolerance of uncertainty were correlated with the frequency of compulsive checking, the relationship between responsibility and checking was fully mediated by intolerance of uncertainty. Implications for the understanding of the relationship between these constructs, as well for conceptualisation of clinical checking problems are discussed.