Background: Retirement is a challenge for veterans during their life course. The aim of this study was to investigate the effect of educational intervention on the perception of aging and social adjustment during retirement. Methods: This quasi-experimental study was performed on 100 military retirees in Shiraz, Iran. Data collection tools included a demographic questionnaire, Perception of Aging, and Social Adjustment. The educational intervention used included six training sessions on the subject of mindfulness, physical and psychological changes of aging, health and self-care management, attitudes toward aging, and social and family relationships in old age. Data were collected at the beginning of the study and two months after the intervention and then analyzed using SPSS version 25. Results: The results showed no significant difference between the control and intervention groups in terms of demographic variables, perception of aging, and social adjustment before the educational intervention. However, the perception of aging significantly decreased, and social adjustment increased in the intervention group after the educational intervention. Improving the perception of aging and parents' perceived role can positively affect social adjustment. Multiple regression analysis indicated a predictive model for social adjustment in later life. Conclusions: With increased knowledge of the retirees on self-care, their perceptions of aging and their role in later life improved and predicte social adjustment.