Extensive research shows university students experience high levels of stress, which can lead to the development of mental health problems such as anxiety and depression. Preliminary evidence supports the role of psychosocial factors such as perceived social support (PSS) and campus connectedness (CC) as protective factors in the development of mental health problems in university students. However, research conducted on the potential ameliorating effects of social support on stress applying Cohen and Wills' (1985) stress-buffering hypothesis produced weak, inconsistent, and even contradictory results. In addition, little attention has been given to examining the protective role of CC in the relationships between perceived stress, anxiety, and depression. The current study examined the applicability of CC and PSS in buffering the relationships been perceived stress, anxiety, and depression across an international sample comprised of university students (N = 206) from Australia, Hong Kong, and the United States. The prediction that CC and PSS would moderate the relationships between perceived stress, anxiety, and depression was partially supported. The results indicated CC moderated the relationship between perceived stress and depression but did not moderate the relationship between perceived stress and anxiety. PSS did not moderate the relationship between perceived stress and depression or the relationship between perceived stress and anxiety, thus rejecting the stress-buffering hypothesis. These findings suggest less emphasis should be placed on PSS as a protective factor, with universities focusing on enhancing CC to reduce the high prevalence of mental health problems to promote psychological wellbeing among students.