This study examined the incremental validity of different information and communication technologies (ICT)-related person characteristics over and above intelligence and and prior achievement when predicting ICT literacy across a period of three years. Relative weights analyses were performed to determine the relative contribution of each predictor towards explaining variance in ICT literacy. We used data from German NEPS that tracks representative samples of German students across their school careers. The sample consisted of 14,436 fifteen-year-old German students who provided self-reports on several ICT-related variables: self-confidence, usage motives, breadth of usage, access, experience, usage at home and at school. Data were analyzed cross-sectionally and longitudinally with structural equation models and path analyses, respectively. Cross-sectionally, all ICT-related variables incrementally predicted ICT literacy after controlling for intelligence (explained variance: 0.4%-14.1%). Longitudinally, ICT self-confidence, ICT-related usage motives, breadth of ICT usage, ICT usage at school, and ICT experience incrementally predict ICT literacy after controlling for intelligence and prior achievement three years later (explained variance: 0.3%-8.1%). Relative weights providing estimates of relative importance of each predictor showed that intelligence (cross-sectional) and prior achievement and intelligence, respectively (longitudinal) explained the largest portion of variance in ICT literacy, followed by ICT self-confidence, and ICT usage motives as the strongest ICT-related variables. These results emphasize that ICT-related motivational constructs play an important role in the development of ICT literacy.