While infusion of technology into schools has been one of the top priorities of the education reform agenda across the world, findings from many large-scale international assessments indicate that students' use of information and communication technology (ICT) has mixed effects on their academic achievements. In this paper, we argue that these ambivalent findings were due to the oversight of the indirect effects of ICT use mediated by other ICT-related variables. We employed multilevel structural equation modelling to unfold the relationship between students' ICT use and their academic achievements based on PISA 2015 data. The results indicated that students' autonomy in ICT use and students' interest in ICT use were found to have significant positive direct effects on students' academic achievements at both within-school and between-school levels. These two variables played a significant role in mediating the indirect effects of ICT use outside school for schoolwork and ICT resources on students' academic achievements. On the contrary, ICT resources and ICT use at school exerted either no direct effect or a negative direct effect on students' academic achievements and students' perceived autonomy related to ICT use, suggesting that mere provision and use of ICT resources in school did not necessarily guarantee success in student performance. At the school level, school's transformational leadership and collaborative climate helped promote students' autonomy in ICT use.