The present study aimed to examine the mediating role of ego-strength in the relationship between religious health behaviors and mental health symptoms during the COVID-19 pandemic in Iran. A total of 346 university students (301 women, 45 men) completed the Ego-Strength Scale, Religious Health Promoting Behaviors Inventory, and Mental Health Inventory from May 2021 to August 2021. The structural equation modeling and the Pearson correlation method were used. The results revealed that religious health behaviors have a positive and significant relationship with, psychological well- being, and ego-strength, as well as a negative significant relationship with psychological distress. The results also showed ego-strength has a negative relationship with psychological distress. Ego-strength mediated the relationship between religious health behaviors and symptoms of mental health. Ego-strength can be considered as a very important variable in religious health psychology; reinforcing ego-strength may have some implications for mental health during the Covid-19 pandemic.