School districts are increasingly adopting 1-to-1 technology initiatives to support 21st century teaching and learning; yet, there are still many challenges with the effective integration of technology into teacher instructional practices. Teacher's technological, pedagogical, content knowledge (TPACK) is an integral part in planning the instructional process for effective integration. In this quantitative study, teachers' knowledge of technology, content, and pedagogy was examined through the lens of TPACK and its relationship to their lesson design practices. Two validated TPACK instruments were used to collect data on 117 in-service teachers in a large, urban school district with a 1-to-1 technology initiative. A MANOVA and correlational analysis were performed, and results of this study indicated there were no statistically significant differences between teachers' constructs of TPACK and their years of experience in a 1-to-1 technology initiative. However, statistical significance was found between teachers' constructs of TPACK and their content area. Additionally, a correlation was found between teachers' TPACK, their lesson design practices, and design disposition. The results of this study may positively impact social change by informing school administrators and other educational change leaders in the planning of teacher instructional support to further develop teachers in the implementation of technology integration to support the 21st century learning needs of today's students.