Depression in mothers is consistently associated with reduced caregiving sensitivity and greater infant negative affect expression. The current article examined the real-time behavioral mechanisms underlying these associations using Granger causality time series analyses in a sample of mothers (N = 194; 86.60% White) at elevated risk for depression and their 3-month-old infants (46.40% female) living in a major metropolitan area in the United States. Overall, mothers contingently responded to infant distress, and mothers' responses to infant distress increased the likelihood of infant soothing in real time. However, there was no evidence for maternal contingent responding or facilitation of infant soothing in subsamples of mothers who were currently experiencing elevated depression symptoms or in mothers of highly negative infants. These findings suggest real-time behavioral mechanisms by which risks for maladaptive self-regulation may develop.