The aim of this study was to examine coparenting perceptions of support and trust as a link between marital quality and parent-child relationship quality. Mothers and fathers with 33-month-old children (n = 122, 61 girls) independently reported on coparenting support and trust, marital quality, and attachment-relevant aspects of the parent-child relationship. Additionally, child-mother attachment security was assessed observationally. Marital quality was related to higher quality mother-son relationships (self-reported and observed) via more positive maternal coparenting perceptions, and marital quality was related to greater father-son and father-daughter relationship quality via more positive paternal coparenting perceptions. For partner effects, marital quality was related to higher mother-son relationship quality via fathers' perceptions of coparenting. Results highlight perceptions of coparenting of both mothers and fathers as a link between marital quality and mother-child relationship quality for families with toddler-aged boys. Further, findings suggest that marital quality fosters more positive paternal coparenting trust and support, which in turn has positive implications for father-son and father-daughter relationships during toddlerhood.