The transition to parenthood brings with it challenges to a couple’s relationship, which in turn are likely to negatively impact coparenting and overall family process. The focus of the current study was to examine the effects of the Bringing Baby Home psycho-educational intervention at the first postintervention follow-up for promoting positive coparenting and family process within the mother–father–baby family system. Expectant parents (N = 181) were recruited from the greater Seattle area to participate in a longitudinal random clinical trials study. Families were randomly assigned to a control, workshop, or workshop plus support group. Observational coding indexed both parent and baby contribution to family interaction during the Lausanne Triadic Play procedure. Principal components analysis was used to create summary factors describing the family play. Results of intent-to-treat analyses indicated that the Bringing Baby Home program was successful in promoting less competition during family play. There also was an effect of workshop timing, suggesting that fathers who took the workshop prebirth were less likely to exhibit intrusiveness during mother–baby focused play than those who received it postbirth. Implications for promoting the formation of positive family-level relations are discussed.