The study presented in this paper was designed to examine Greek primary education teachers' perceptions of their knowledge and skills with regards to the integration of ICT in their instructional practices. By adopting the Technological Pedagogical Content Knowledge framework, we developed an extended TPACK scale, including two sub-constructs, i.e., (a) the Educational Context and (b) teachers' self-assessment of TPACK abilities. The analysis of the results showed that the participants appear to believe that they have a good level of knowledge with regards to the primary TPACK domains, i.e., content, pedagogy and technology. However, most teachers perceived them separately and were not able to integrate their TPACK knowledge in order to design and implement meaningful ICT-based interventions in their classroom practice. Statistically significant differences were recorded in relation to teachers' factors, i.e., gender, teaching experience and training about ICT in education. Finally, the findings showed that teachers' efforts to implement ICT-based interventions in their classrooms could be affected by factors related to the educational context in the Greek primary schools.