Research has demonstrated consistently that personality and perceived stress, independently, are essential factors for university adjustment among university freshmen; however, little is known about the associations between personality, perceived stress, and adjustment together. Our primary goal was to explore the predictive utility of perceived stress for explaining university adjustment among university freshmen (N = 290). We also tested the moderating role of personality traits and this research was embedded within a Big Five model of personality including the sixth trait for Turkish context, 'Negative Valence'. Results addressed that only conscientiousness and negative valence moderated the perceived stress and adjustment association. Students high on negative valence and/or conscientiousness tended to experience the detrimental effect of perceived stress on university adjustment more due to their personality. These results suggested that personality might be an important factor to include in adjustment fostering interventions for freshmen at universities.