Worldwide, many children experience parental separation and divorce. This has a significant impact on their well-being, and emotional and behavioral functioning, and calls for prevention. To assess the effects of the Children of Divorce Intervention Program in the Netherlands (CODIP-NL) on 6- to 8-year-olds, we performed a quasi-experimental effect study. The study compared children receiving CODIP-NL (intervention: I, n = 104), children not receiving CODIP-NL but having divorced parents (divorced control: DC, n = 37), and children belonging to non-divorced families (non-divorced control: NDC, n = 138). Outcomes pertained to children's positive functioning, emotional and behavioral problems, and well-being. We assessed pre- to post-test differences in change in mother-reported outcomes between the intervention and control groups, and pre- to post-test differences in group leader reports. The intervention led to increases in mother-reported positive functioning (d = 0.97 I vs. DC; d = 1.04 I vs. NDC), and well-being (d = 1.00 I vs. DC; d = 0.84 I vs. NDC). Mother-reported child emotional and behavioral problems decreased after participation (total difficulties, d = 0.73 I vs. DC; d = 0.49 I vs. NDC). Group leader-reported pre- to post-test differences (p