Sleeping problems in young children are very common, affecting up to 20% of 1-year-olds. Behaviour therapy is the most widely recognised treatment but a significant proportion of parents find it aversive. This suggests that parental cognitions may be important and underevaluated. The aims of this study were therefore fourfold: (1) to describe the development of a new tool to measure maternal cognitions in relation to infant sleeping problems, the Maternal Cognitions about Infant Sleep Questionnaire (MCISQ); (2) to assess the psychometric properties of the MCISQ; (3) to test the hypothesis that maternal cognitions will be associated with, and specific to, infant sleep problems; and (4) to discuss the implications of the findings with respect to aetiological models of infant sleep problems, treatment, and future research. Results showed that maternal cognitions about setting limits, anger at the infant's demands, and doubts about parenting competence were significantly associated with infant sleep problems, whereas cognitions about infant hunger or cot death were not. It is hypothesised that these cognitive responses, if extreme, may disrupt sensitive parent–child interactions, which over time could lead to impairments in the development of infant self-regulation.