The present study was conducted to investigate the efficacy of unified trans-diagnostic treatment on marital disaffection and differentiation in the veterans’ wives. It was a quasi-experimental study with pretest, posttest and control group design and two-month follow-up period. The statistical population of the present study included the wives of the veterans with neurological and psychological complications in the city of Tehran from May to July of 2020. 30 veterans’ wives were selected through voluntary sampling method and randomly accommodated into experimental and control groups (each group of 15 women). 27 women (13 in the experimental group and 14 in the control group) remained after the exclusion. The experimental group received ten ninety-minute sessions of unified trans-diagnostic treatment (Barlo et.al, 2011) during two-and-a-half months. The applied questionnaires in this study included marital disaffection questionnaire (Pines, 1996) differentiation questionnaire (Drake, 2011). The data were analyzed through mixed ANOVA via SPSS23 software. The results showed that the unified trans-diagnostic treatment has had significant effect on the marital disaffection and differentiation of the veteran’s wives (p<0.001) and led to the improvement of their marital disaffection and differentiation. According to the present study it can be concluded that the unified trans-diagnostic treatment can be applied as an efficient therapy to improve marital disaffection and differentiation of the veterans’ wives.