In the transition from secondary to tertiary education, first-year students experience stress due to the academic, cultural, and social environment they must adapt to. This may negatively impact their subjective well-being, which in turn may negatively influence academic performance and increase the probability of dropping out. We report findings from a two-wave online study involving first-year students enrolled in a sociology course at the Faculty of Psychology and Educational Sciences at the University of Leuven (Belgium). Students completed self-report questionnaires on sociodemographic background, subjective well-being, parental relationship quality, and personality, at the start (Time 1) and end (Time 2) of the first semester. 194 students (35%) completed measures at both times. Results show that subjective well-being decreased from the beginning to the end of the first semester. Well-being at university was positively, and feelings of depression negatively, related to subjective well-being at Time 1 and Time 2. Female students reported lower well-being than male students at Time 2 but not Time 1. The quality of the mother–child, but not the father–child, relationship was positively related to subjective well-being at Time 1 and Time 2.