This study examines the mediating role of Perceived Stress related to Covid-19 in the relationship between Intolerance of Uncertainty IU and Subjective Wellbeing and the differences in Psychological Wellbeing attributed to demographic variables. For this aim the researcher has translated three measures into Arabic language and administered them to (460) Egyptian adults between (22- 60) years, with mean age (33,19) and standard deviation (11,70). The measures were the COVID-PSS-10, (by Pedrozo-Pupo et al., 2020), the short version of the Intolerance of Uncertainty Scale (IUS-12), (by Carleton, Norton, & Asmundson, 2007), The Five Well-Being Index (WHO-5). Results showed significant negative correlation between both IU and Perceived Stress related to Covid-19 and Subjective wellbeing. A significant positive correlation was found between IU and Perceived Stress related to Covid-19. There were statistically signigicant group differences attributed to gender, work status, and marital status but not age. Path analysis results showed a partial mediating role of Perceived Stress related to Covid-19 in the relationship between IU and Subjective Wellbeing.