Emphasis on continuous infant sleep overnight may be driven by parental concern of risk to child mental health outcomes. The Mercy Pregnancy and Emotional Wellbeing Study (MPEWS) examined whether infant sleep at 6 and 12 months postpartum predicts anxiety disorders at 2-4 years, and whether this is moderated by maternal depression, active physical comforting (APC) or maternal cognitions about infant sleep. Data included 349 women and infants. Infant sleep was measured using the Brief Infant Sleep Questionnaire and child anxiety disorders by the Preschool Age Psychiatric Assessment. The risk of developing generalised anxiety or social phobia disorders at 3-4 years was reduced by 42% (p = 0.001) and 31% (p = 0.001), respectively, for a one standard deviation increase in total sleep at 12 months. No other infant sleep outcomes were associated. Maternal depression, APC and cognitions about infant sleep did not significantly moderate these relationships. Focus may need to be on total infant sleep, rather than when sleep is achieved.