The transition to university can be challenging not only for the general student population but also for LGBTQ+ students, whose social experiences may be particularly demanding. In the current research, we explore first-year students' perceptions of belonging and social adjustment by (a) estimating whether such perceptions relate to achievement motivation, well-being, and academic performance and (b) identifying whether these trends differ for LGBTQ+ students. First-year students from one public university in New Zealand (n = 896) completed a questionnaire to report their early experiences in higher education. Grade Point Average (GPA) was provided by the institution. Results using descriptive statistics and regression-based, moderation models offer empirical support that belongingness and social adjustment have the potential to impact first-year students in meaningful ways, and that some of these patterns vary between LGBTQ+ and non-LGBTQ+ students. Individuals who reported institutional belonging and felt as though they had adjusted well to university also reported high levels of achievement motivation and well-being. Meanwhile, individuals who reported peer belonging were linked to weaker achievement motivation yet a "higher" GPA. Our results introduce new evidence that although LGBTQ+ students reported relatively poorer well-being, they experienced relatively more enjoyment and less boredom in their classes. Interactions from moderation testing reveal that the statistical predictions of belongingness and social adjustment for academic self-efficacy and subjective well-being differed between LGBTQ+ and non-LGBTQ+ students. We discuss the practical implications of our results and identify ways for higher educational institutions to support first-year students.