This study sought to assess the effectiveness of a marital distress prevention program for couples by examining how marital quality, especially marital competencies such as dyadic coping, could be improved by means of a prevention program focusing on the enhancement of coping resources (Couples Coping Enhancement Training). The study consisted of 59 couples in the intervention group and 59 couples in the matched comparison group. The results reveal that it is possible to improve marital quality, especially marital competencies, by means of one short-term intervention lasting 18 hr. However, the effects decreased after 2 years, raising the importance of booster sessions in helping to maintain effects over a longer period of time.