This qualitative cross-case study explores the influence of a designed learning trajectory on transforming teachers' technological pedagogical content knowledge (TPACK) for teaching with digital image and video technologies. The TPACK Learning Trajectory embeds tasks with specific instructional strategies within a social metacognitive constructivist structure to engage K-12 in-service teachers in an online learning course for teaching and learning mathematics and science with these technologies. The resulting trajectory shapes teachers' TPACK into a more robust, integrated knowledge structure, influencing their thinking and decision making about the content, technology, and pedagogical concerns with these technologies. From their learning experiences, the teachers' instructional intentions transformed to incorporate the tools and processes for teaching with technologies. The TPACK Learning Trajectory thus influences a transformation in the teachers' TPACK strategic thinking about when, where, and how to use the technologies, with potential for influencing students' thinking and learning of the content.