This mixed-methods study analyzed Technological Pedagogical Content Knowledge (TPACK) learning trajectories of preservice teachers enrolled in an online seven-week long educational technology course. Timeline analysis was used to identify and interpret emerged patterns of learning trajectories. The study suggests that continuous growth of the group mean TPACK could be attributed to the inclusion of immersion - theory - analysis - digital content development cycles, focus on high-impact teaching strategies, and a choice of interactive online platform. Level of participation, support from the instructors, and confidence in using technology for teaching and learning moderated the course influence leading to several distinct patterns in individual TPACK learning trajectories.