The extent to which mother and infant sleep predict maternal sensitivity as (a) main effects and (b) moderate the association between social cognition about infant crying (i.e., cry processing) and maternal sensitivity was examined in a sample of 299 mother-infant dyads (43% of mothers non-White; 50.5% of infants female). Infant- and mother-oriented cry processing were assessed prenatally using a video recall procedure and mothers self-reported demographics and characteristics reflecting emotional risk. When infants were 2 months old, mothers reported their depressive symptoms and mother and infant sleep. Maternal sensitivity and infant negative mood were observed during free play and the still face. There were no main effects of mother or infant sleep on maternal sensitivity over and above covariates. However, infant total sleep duration across night and day and mother sleep disturbance moderated the effect of mother-oriented cry processing on sensitivity. Specifically, mother-oriented cry processing was associated with lower maternal sensitivity only among mothers whose infants had lower sleep duration and who reported more sleep disturbances. Moderating effects were not apparent for infant night wakings or time awake or mothers' total sleep problems. Constrained opportunities for sleep or respite across the entire day and the totality of mothers' nighttime sleep disturbances, not just those specific to infants' night wakings, undermine maternal sensitivity by exacerbating mothers' preexisting tendency to have self-focused and negative reactions to infant distress. The efficacy of interventions designed to facilitate maternal sensitivity and infant adjustment may be enhanced by adding targeted foci on maternal and infant sleep. (PsycInfo Database Record (c) 2024 APA, all rights reserved).