This research surveyed three hundred and ninety pre-service and three hundred and ninety four in-service teachers with regards to the seven factors of technological pedagogical content knowledge, their beliefs about constructivist oriented teaching (CB) and design disposition (DD). Both exploratory and confirmatory factor analyses showed that the survey based on the nine-factor model had high reliability and validity. Significant differences between pre-service and in-service teachers in the TPACK factors and CB and DD were found and the differences reveal that the pre-service teachers are less knowledgeable and confident with regards to all the factors. In order to identify predictors of TPACK, the research further explores the relationships among TPACK factors, CB and DD through structural equation models. The findings reveal that DD consistently predict both pre-service and in-service teachers' TPACK and this provide support about the importance of design disposition for TPACK advancement. However, CB does not predict the pre-service teachers' TPACK. In addition, CB is a significantly negative predictor for the in-service teachers' TPACK. The findings may imply that while the inservice teachers believe strongly in constructivist oriented teaching, they need further professional development in designing instruction to actualize their desired form of education.