Toddler sleep problems have a major impact on mothers’ sleep, putting mothers at risk for shortened nighttime sleep and psychological difficulties. The mechanism of how toddler sleep problems affect maternal psychopathology (i.e. depressive/anxiety symptoms) has not been explored in a cohesive model, particularly among low-income populations. Low-income families frequently co-sleep, a practice that affects both maternal and toddler sleep duration/quality. The purpose of this analysis is to examine relations between toddler/maternal sleep, including co-sleeping practices, and maternal symptoms of psychopathology, in mothers of low-income toddlers; a population at risk for both poor sleep and mental health problems. We hypothesize that shortened maternal sleep duration mediates relations between toddlers sleep problems and maternal anxiety/depressive symptoms. This study utilizes baseline data from low-income mothers of toddlers (ages 12–32 months) who participated in a parenting intervention. Mothers provided demographic information and completed questionnaires on their toddler’s sleep (Brief Infant Sleep Questionnaire, BISQ), their own sleep (Pittsburgh Sleep Quality Index, PSQI) and their mental health symptoms (State-Trait Anxiety Inventory, STAI; Beck Depression Inventory, BDI). Moderated mediation models were conducted to predict maternal symptoms of anxiety/depression using the SPSS macro PROCESS, controlling for poverty level. Sample included 282 mothers, 68% African American, 70% living below the poverty threshold, and 61% co-slept with their toddler. The differences in indirect effects by sleep arrangement were tested in separate models for maternal symptoms of depression and anxiety, respectively. The results showed that toddlers sleep arrangement moderated the mediation effects of maternal sleep duration on the relationship between toddler sleep problems and maternal symptoms of depression (diff= 1.10, 95% bootstrapped CI: .21, 2.46) and anxiety (diff.= .44, 95% BCI: .08, 1.07). Further analysis showed significant mediation effects for depression (mediation effect= .87, CI: .22-1.84) and anxiety (mediation effect= .35 CI: .08-.84) for mothers of toddlers who co-slept, but not of those who slept by themselves. Findings support the hypothesis that among co-sleeping families, the relation between toddler sleep problems and maternal psychopathology is explained by shortened nighttime sleep. Further investigations should examine whether these relationships exist longitudinally between mothers and toddlers. none.