Introduction: Facial deformities and aesthetic and functional anomalies in children may be a cause of real distress in families. Problems faced by parents in coping with a child’s anomaly can be upsetting and lead parents to exhibit over-severe behavior. The present study was conducted in order to study the effect of happiness program on the happiness of the mothers of children with a cleft lip and palate.   Materials and Methods: In this semi-experimental study, 64 mothers of children with a cleft lip and palate enrolled by convenience random sampling were assigned to an intervention or control group based on a simple random sampling. Then, a program of happiness training was implemented consisting of 10 sessions of 2 hours each. A demographic questionnaire and the Oxford Happiness Questionnaire were completed prior to and 2 months after the last session of intervention. The data were analyzed using descriptive and analytical statistics, consisting of a paired t-test, independent t-test and Chi-square test using SPSS version 20.   Results: The independent t-test indicated a significant difference in mean happiness score after training between the intervention and control groups (P0.05).   Conclusion: In light of the efficacy of happiness training on the promotion of happiness in the mothers of children with a cleft lip and palate, this model is recommended as a healthcare intervention to decrease stress in mothers following the birth of an infant with a cleft lip and palate.