This longitudinal study examined the development of mother-infant objective and reported sleep quality and duration in solo-mother families (i.e., mothers who decided to parent alone) in comparison to two-parent families. We recruited 134 solo mothers and 161 married mothers during pregnancy, most representing the middle to upper socioeconomic class in Israel. Assessments were conducted during pregnancy and at 4 and 8 months postpartum. Maternal and infant sleep were assessed with actigraphy and sleep diaries for 7 nights. Questionnaires were used to assess maternal insomnia symptoms, sleepiness, sleeping arrangements, and background variables. The comparison of sleep between solo-mother and two-parent families, at each assessment point, showed no differences in sleep duration, and only a few differences in sleep quality measures; these were partially explained by maternal age and breastfeeding. Nevertheless, solo mothers were more likely to share a bed with their infants. In both groups, trajectory analyses showed a decrease in maternal actigraphic and diary sleep quality measures from pregnancy to 4 months, followed by an increase from 4 to 8 months. However, maternal insomnia symptoms first declined, and then increased, and maternal sleep duration first lengthened and then shortened. Infant actigraphic and diary sleep quality increased in both groups from 4 to 8 months, whereas sleep duration decreased only in the "solo" group. In general, the findings suggest that objective and subjective sleep quality and sleep duration of solo-mother families, a growing yet unexplored family structure, do not seem to be significantly affected by the absence of a second parent.