This paper provides a meta-analytic examination of strength and direction of association between parents’ couple relationship quality and early childhood attachment security (5 years and under). A comprehensive search of four EBSCOhost databases, Informit, Web of Science, and grey literature yielded 24 studies meeting eligibility criteria. Heterogeneity of the couple quality construct and measurement was marked. To disaggregate potentially differentially acting factors, we grouped homogeneous studies, creating two predictor variables defined as “positive dyadic adjustment” and “inter-parental conflict”. Associations of each construct with offspring attachment security were examined in two separate meta-analyses. Inter-parental conflict was inversely associated (8 studies, k = 17, r = −0.28, CI = [−0.39 to −0.18]), and dyadic adjustment was not associated with offspring attachment security (5 studies, k = 12, r = 0.14, CI = [−0.03 to 0.32]). The study supports finer distinctions of couple relationship constructs and measurement in developmental research, assessment, and intervention.