This study investigated whether a psycho-educational program with modest dosage (eight sessions), delivered in a universal framework through childbirth education programs and targeting the coparenting relationship would have a positive impact on observed family interaction and child behavior at 6-month follow-up (child age 1 year). One hundred sixty-nine couples, randomized to intervention and control conditions, participated in videotaped family observation tasks at pretest (during pregnancy) and at child age 1 year (2003-2007). Coparenting, parenting, couple relationship, and child self-regulatory behaviors were coded by teams of raters. Intent-to-treat analyses of program effects controlled for age, education, and social desirability. Evidence of significant (p < 0.05) program effects at follow-up emerged in all four domains. Effect sizes ranged from 0.28 to 1.01. Targeting the coparenting relationship at the transition to parenthood represents an effective, non-stigmatizing means of promoting parenting quality and child adjustment.