Older adults with Alzheimer’s disease (AD) experience drastic changes in their physical and mental abilities. AD patients became heavily dependent on their caregivers for everyday functions, which have significant implications not only for them but also for their caregivers. So, many ADcaregivers experiencedan increased level of depression and anxiety symptoms, lower perceived control, and higher burden compared to non-AD caregivers.Therefore, psychological first aid (PFA) and educational interventions are designed to enable those caregivers to meet the daily requirements of their patient care and to cope with its challenges.Aim: determine the effect of psychological first aid program on stress level and psychological well-being among caregivers of older adults with Alzheimer's disease. Design a quasi-experimental research design (one group pre-test post-test)was followed. Subjects:A convenience sample of one hundred (100) caregivers of older adults with AD.Setting: all online groups concerned with the care of Alzheimer’s disease patients on Facebook. Tools: Socio-demographic and clinical data of older adults with Alzheimer's disease and their caregivers’questionnaire,Alzheimer's disease knowledge scale, Kingston caregiver stress scale, and authentic identity measures (AIM) scale of psychological well-being. Results: the psychological first aid program has highly statistically significant effect on the AD caregivers’ knowledge, stress level and psychological well-being as (t=-30.707, P= 0.000, t=8.500, P= 0.000 & t= -4.763, P=0.000 respectively).Conclusion: psychological first aid program is considered an effective intervention in decreasing the AD caregivers’ stress and increasing their psychological wellbeing and knowledge regarding delivering care for AD patients.