Family-focused prevention programs for community samples have potentially broad, clinically relevant implications but few studies have examined whether any program benefits continue to be observed over the long term. Although benefits of a marital conflict focused parent education program, the Happy Couples and Happy Kids (i.e., HCHK) program, were supported in a study based on pre-test, post-test, 6-month follow-up, and 1-year follow-up assessments, the longer-term stability of treatment effects has not been established. Couples with children between 4 and 8 years of age who had previously participated in the HCHK study completed a two-year follow-up, including a parent-only group (PO, n=12); parent-child group (PC, n=15); and a self-study group (SS, n=12). Greater knowledge about the effects of marital conflict on families and behavioral improvements in constructive conflict, and specifically in problem-solving behaviors, were observed at the two-year follow-up for couples who received the HCHK program. Reflecting an innovative analysis of mediating mechanisms, change-to-change analyses showed that these changes were linked with improvements in other family processes over time, including marital satisfaction, parenting and child adjustment. The findings support the relatively long-term efficacy of brief, psychoeducational programs for educating community samples about marital conflict and family processes. (Contains 1 figure and 4 tables.)