Abstract Background: The mental health of the parents of Autism Spectrum Disorder (ASD), particularly the mothers, is poor due to the severity and complex nature of this condition, and they encounter numerous issues. This investigation aimed to determine whether happiness education affected mothers of children with ASD’s Expressed Emotions (EE) and Quality of Life (QoL). Materials and Methods: A total of 70 mothers of children with ASD aged 3 to 13 years participated in this clinical trial study research. The experimental group received the Fordyce happiness training program once every 6 weeks via WhatsApp. In three stages, data were collected using a demographic form, the Family Questionnaire (FQ), and the World Health Organization Quality Of Life Instrument, Short Form (WHOQOL-BREF) (before the intervention, immediately afterward, and 1 month later). In the Statistical Package for Social Sciences (SPSS) software, the acquired data were analyzed using independent-sample t-tests, Chi-square tests, and repeated-measures Analysis of Variance (ANOVA). Results: There was no significant difference in EE and QoL mean scores between the two groups before the intervention, but after, the intervention group’s mean score of EE (20.91 (4.355)) was substantially lower than the control group’s (44.74 (4.77)) (p < 0.001). In comparison, the intervention group’s mean score of QoL and its dimensions was more significant than the control group’s (p < 0.001). Conclusions: Given the efficacy of the happiness education program in reducing EE and enhancing QoL in mothers of children with ASD, such treatment strategies should be developed and used.