Unwanted pregnancy has many negative consequences in terms of women's physical and mental health. Resilience is a process of utilizing important resources to maintain mental health in the face of stress. In addition, resilience can be promoted through. This study was performed to evaluate the effect of resiliency training on the mental health and resilience of pregnant women with an unwanted pregnancy. This randomized clinical trial was conducted on 66 women in Sabzevar, Iran, in 2020 with unwanted pregnancies, mild or moderate mental health problems, and low resilience. The participants were randomly divided into two groups through a simple lottery. In the intervention group, resilience training was performed once a week in groups of 10-15 people in six training sessions, each lasting 60 to 90 minutes. Mental health and tolerability were measured using the 28-item General Health Questionnaire and the Connor-Davidson Resilience scale before the intervention, and immediately after and 1 month after the intervention. The mean (SD) of mental health immediately 35.46 (5.59) and 1 month after the intervention 33.73 (3.85) in the intervention group (F = 91.23; p < 0.001) was reduced significantly compared to the control group (F = 94.02; p < 0.001). The results of the mean (SD) showed that the resilience training intervention significantly increased the resilience score in the intervention group 84.36 (8.49)(compared to the control group (49.13) 6.67)((p < 0.001). Resilience training was effective in promoting the mental health and resilience of pregnant women with unwanted pregnancies.