Introduction: Marital infidelity is one of the intricate and harmful emotional problems among couples. Infidelity in marital relations could be considered as a stressful phenomenon, which results in cognitive, emotional, and behavioral disorder signs in individuals. This study aimed to investigate the effectiveness of acceptance and commitment therapy on stress, anxiety, and depression improvement in females, who had experienced infidelity in marital relations in Sanandaj City.

Methods: This was a semi-experimental study, which used pre-test, post-test design on the control group. The sample size was 30 females, who had experienced infidelity in their marital relations, and were attending the family court of Sanandaj City, during year 2015. They were allocated based on convenience and random sampling to two groups (15 control and 15 experimental). Research tools were depression short inventory, anxiety, stress (DASS-21) and interruptive group therapy based on acceptance and commitment therapy, accomplished during 12 treatment sessions of 90 minutes on the basis of weekly routines. In order to analyze the data on descriptive level, the researchers used mean statistics and standard deviation, and in inferential level, the researchers used One-way Analysis of Covariance Test (ANCOVA).

Results: Interruptive group therapy method based on acceptance and commitment directly decreased and improved stress signs, anxiety and depression of females under the study (P < 0.005).

Conclusions: Findings of this study indicate the importance and effectiveness of treatment based on acceptance and commitment to reduce stress, anxiety and depression of females, who had experienced infidelity in marital relations. Therefore, this kind of therapy could be used to decrease and improve infidelity’s harmful effects in marital relations.