This study examined the association between infant sleeping arrangements (i.e., habitual co-sleeping, inconsistent co-sleeping, and non-co-sleeping) and quality of mother–infant interaction during play in a sample of mothers, each with a typically developing infant (N=70). Mother–infant dyads who experienced consistency in infant sleeping arrangements in a typical week at 6 months (i.e., habitual co-sleeping or non-co-sleeping) were characterized by more positive maternal and infant behavior and dyadic quality of interaction at 9 months compared with dyads who experienced inconsistency in sleeping arrangements. Additionally, a greater amount of co-sleeping per week was associated with an increased duration of breastfeeding, mothers working fewer hours, less infant temperamental intensity, and less maternal depression. This study underscores the advantages of empirically based studies that consider consistency in infant sleep experience as a factor that is associated with more positive mother–child interaction.