Ample research exists on barriers to the use of computers as a form of information and communication technologies (ICTs) in teaching. The most common barrier reported to prevent teachers from using computers in teaching is the lack of resources. However when resources are available, ICTs are still often not effectively integrated into teaching. This study explored how teacher beliefs relate to the use of ICTs for three purposefully selected teachers of Natural Sciences in a public school well resourced for ICT. This study, therefore, considered under-explored intrinsic factors that contribute to ICT usage in a technology-rich context. The theoretical framework for this study merged the Hew and Brush model with the Vickers Framework which shows the relationships among various factors, including beliefs about the pedagogical use of technology, that affect the use of ICTs in teaching and learning. A qualitative, multiple case study approach was used and data were collected using questionnaires, lesson observations and semi-structured interviews. The lesson observations and interviews were recorded and transcribed in full. The analysis of data involved coding and thematic categorisation for each case and across cases. The findings suggest that within a technology-rich context, extrinsic factors play a minor role whereas the intrinsic factor, namely beliefs, plays a major role in teachers' ways of using ICTs in science teaching. Beliefs emerge and are influenced by three factors, namely, value judgement, reality judgement and action judgement. Value judgements, such as those based on the beliefs about the important role of the teacher and beliefs about the nature of teaching, have the largest influence on the way teachers use ICTs in the classroom, while reality judgements and action judgements are also influential to an extent. The study recommends that ICT use in schooling still needs consistent support in cultivating positive ICT-related teacher beliefs and that further research on intrinsic barriers encountered in technology-rich contexts is required.