The technological, pedagogical, and content knowledge (TPACK) framework has been regarded as potentially effective in helping teachers integrate technology into the classroom. This study explores the instructional strategies of teachers when developing TPACK. A teacher professional development (TPD) program, in which teaching activities and deep discussions were key processes, was conducted. Instructional observations and focus-group interviews were the primary evaluation methods. Six elementary school teachers participated in this program between September 2011 and January 2012. Analytical findings demonstrate that teachers initially had limited pedagogical knowledge (PK). For intentional use of technology during teaching, the teachers transformed technology operating skills into multiple teaching activities for content learning, and expanding their TPACK base. The teachers then applied PK basis and combined them with subject content and technology through the TPD program, and reorganized their application of TPACK. Moreover, teachers engaged in peer observation and group interviews during TPD, effectively built TPACK. This study provides teacher educators who are interested in examining teachers' TPACK with an effective TPD program for technology integration. We recommend that teacher educators continually enhance the technological knowledge of teachers and promote TPACK through collaborative TPD programs.