Loneliness may affect children’s psychological well-being and academic achievement. Parent-child relationships have been consistently associated with child adjustment. However, parental antecedents of child loneliness have been relatively understudied. Guided by attachment theory, we examined the trajectories of father-child and mother-child relationship closeness and conflict, and their associations with trajectories of child loneliness with National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development (SECCYD) data to understand parents’ roles in child loneliness in middle childhood. In Grades 1 (Mage = 6.57, SD = .29), 3, 4, and 5, both resident fathers and mothers reported on parent-child relationships. At Grades 1, 3, and 5, children reported on their loneliness. Loneliness declined from Grade 1 to Grade 5. After controlling for socioeconomic status (SES), the slope of father-child relationship closeness was negatively associated with the slope of loneliness for girls (n = 341), but not for boys (n = 354). The more slowly father-child closeness declined, the more quickly girls’ loneliness declined. These findings highlight the role of father-child relationships in child loneliness for girls. Future research on child loneliness should take both maternal and paternal roles into consideration.