The aim of this research was to examine the relationship between psychological capital, coping styles (problem-oriented, emotion-oriented and avoidance-oriented) and perceived stress, and to examine the mediating role of coping styles in relation to psychological capital and perceived stress. This cross-sectional study was conducted on a sample of 228 employed individuals. The psychological instruments used in this study were: Perceived Stress Scale (PSS), Psychological Capital Questionnaire (PCQ) and Coping Orientation to Problems Experienced (COPE). The results of this research show a moderate negative correlation between psychological capital and perceived stress. The results revealed a low positive correlation between psychological capital and problem-oriented coping and a low negative correlation between psychological capital and emotion-oriented coping as well as avoidance-oriented coping. Also, a very low negative correlation between problem-oriented coping and perceived stress has been discovered as well as low positive correlation between emotion-oriented coping and avoidance-oriented coping with perceived stress. Furthermore, hierarchical regression analysis has shown that avoidance-oriented coping and psychological capital are significant predictors of perceived stress after controlling gender and age variables, whereby the less frequent use of avoidance and the higher level of psychological capital predict a lower level of perceived stress. Finally, a partial mediation of an avoidance-oriented coping in the relationship between psychological capital and the perceived level of stress has been established, that is to say that a higher level of psychological capital predicts a less frequent use of the avoidance-oriented coping style, which in turn predicts a significantly lower level of perceived stress.