<p>Biobehavioral synchrony represents a dynamic interpersonal mechanism that influences parent and child depression risk via parent-child interactions, which may operate directly or in concert with depression-related impairments in parenting. We hypothesized that parent depressive symptoms and unsupportive emotion-related socialization behavior (ERSB) would negatively predict positive affect and physiological synchrony, and that these parent factors would moderate the effects of dyadic synchrony on daughters’ depressive symptoms. Eighty parent (87.5% female)-daughter (<i>M</i>_{child age} = 8.26 years, <i>SD</i>_{child age} = 1.51 years; 38.0% White) dyads participated in a 5-minute conflict discussion task, during which second-by-second estimates of parent unsupportive ERSB and parent and daughter affect and respiratory sinus arrhythmia (RSA) were obtained. Parent self-reported depressive symptoms and rated child behavior problems. Contrary to hypotheses, path models suggested that neither parent depressive symptoms nor unsupportive ERSB was associated with dyadic synchrony of positive affect or RSA. However, as expected, parent depressive symptoms and unsupportive ERSB moderated predictions of daughters’ depression symptoms from dyadic synchrony. The nature of these interactive effects depended on the synchrony modality (i.e., positive affect, RSA) and parent factor under investigation. RSA synchrony during parent-daughter conflict discussion buffered against the adverse effects of parent depressive symptoms on daughters. Importantly, these patterns were specific to daughters’ depressive symptoms rather than general dimensions of child psychopathology. These results underscore the centrality of multimodal, dynamic processes through which parent-daughter interactions may shape depression risk in daughters.</p>