Background: During the first years of life, parental sleep strongly depends on child’s sleep quality. Poor parental sleep may relate to increased stress and negative mood. However, there is a lack of sleep studies focusing on all family members. This study aimed to investigate the relationship between sleep, mood, and stress in mothers, fathers and children. Methods: Data were obtained from 65 parental couples and 65 children (2 to 36 months). Data on sleep for all family members and stress of parents were completed by both mothers and fathers through questionnaires and sleep diaries. Results: Toddlers’ positive mood before nocturnal sleep was significantly associated with reduced wake times after sleep onset. Mothers reported worse sleep quality compared to fathers. Shorter sleep onset latency in fathers and better sleep efficiency in mothers were linked with better self-reported mood upon awakening. In mothers, but not in fathers, poor sleep quality was associated with higher perceived stress. Conclusion: Results suggest bidirectional relationships between sleep and mood in children, mothers and fathers. Moreover, results evidence poorer sleep in mothers, compared to fathers, which was linked with increased parenting stress. This gender gap should be further considered in studies with larger samples and in clinical contexts.