The first year of university is one of the most difficult times in a student’s life due to numerous changes that occur. This cross-sectional study explores the concept of parental and peer attachment, which has been researched for its ability to predict students’ success in higher education. Yet, less research has investigated the mechanisms underpinning the relationship between attachment and university adjustment among first-year students. Hence, the aim of this study was to examine the impact of parent and peer attachment on first-year university students, and understand how these attachments can facilitate university adjustment through identity exploration. This investigation is underpinned by Bowlby and Ainsworth’s attachment theory and Arnett’s emerging adulthood theory. Data were collected from 568 first-year students at a public university in Sabah, Malaysia, via adapted questionnaires. Structural equation modelling was employed using SmartPLS Software 3.0 to analyse the data. The study found that identity exploration mediates the relationship between parental trust, peer communication, and university adjustment. The findings of this study provide valuable insights for professionals working with emerging adult clients, especially those in higher education institutions, aiming to enhance the adjustment level among first-year students.