The seven constructs of the technological pedagogical content knowledge (TPACK) framework has been widely adopted as a theoretical basis for understanding the scope of teachers' information and communication technology (ICT) expertise. Despite this, very little is understood about the inter-relationships between these constructs, especially how these relationships are related to teachers' TPACK. As a result, the theory-practice nexus of this framework remains weak. In this study, a structural equation model based on Mishra and Koehler's TPACK framework was developed to describe the TPACK perceptions of 455 practicing teachers in Singapore. The study shows that teachers, perceived TPACK to be formulated from the direct effects of technological knowledge and pedagogical knowledge. They also perceived these knowledge sources to contribute to the development of technological pedagogical knowledge and technological content knowledge, which also contributed to their TPACK. In these teachers' conceptions of TPACK, however, the effects of content knowledge and pedagogical content knowledge were not evident. The implications of these relationships to the design of teacher professional development in ICT are discussed.