In accordance with the Self-Determination Theory, the interpersonal behavior of others can support or thwart the basic psychological needs and influence the well-being of students. Furthermore, several studies have shown that problematic internet use has a negative influence on the academic field. However, no studies have investigated the impact of need-supportive and need-thwarting interpersonal behaviors (using the SDT theoretical framework) on internet addiction, academic engagement, and academic achievement. For this reason, the main purpose of this study is to investigate the relationship between students' perceptions of others' behaviors that supported or thwarted their basic psychological needs, internet addiction, and academic engagement and the impact on academic achievement through two studies. In the first study, 889 students (age: M = 20.26, SD = 3.16), were used to investigate the dimensionality of the Italian version of the Interpersonal Behaviour Questionnaire (IBQ) and the reliability, convergent and concurrent validity. In the second study, 515 students (age: M = 20.26, SD = 3.16) were tested to investigate the mediating role of problematic internet use on the relationship between students' perceptions of others' behaviors that supported or thwarted their basic psychological needs and academic engagement and the impact on academic achievement. The results of the first study suggested that the Italian version of the IBQ shows good psychometric characteristics in the Italian context. The results of the second study confirmed the mediating role of problematic internet use and academic engagement as mediators between students' perceptions of need-thwarting interpersonal behaviors and academic achievement.