Background: Teachers need to support students and prepare them for the digital future by effectively using digital technologies. In this context, improving teachers’ Technological Pedagogical Content Knowledge (TPACK) through online Professional Development (PD) interventions is critical to increasing success in technology integration. Purpose: The current study explores science teachers’ views on TPACK practical, TPACK self-efficacy, levels of Synthesis of Qualitative Data (SQD) strategies, and online completion of PD within the scope of TPACK-based online PD activities in which SQD strategies are integrated. Sample: The participants of the study were science teachers from 14 middle schools. Design and methods: This study was designed using a mixed-method-embedded pattern. A 15-week PD program was conducted with the participants within the scope of SQD strategies (role model, reflection, instructional design, collaboration, real life, feedback) integrated into TPACK-based online PD. Data were collected using various tools in the context of qualitative and quantitative methods. Results: TPACK-based online PD, in which SQD strategies were integrated, had a significant effect on improving science teachers’ TPACK practical, level of use of SQD strategies, and TPACK self-efficacy. Feedback was given to the teachers after the first lesson plans were prepared individually, and after the feedback, more teachers collaboratively used information and communication tools (ICT) in their lesson plans. According to the opinions of science teachers regarding online completion of PD programs, education is useful and efficient in terms of content, participation opportunities, communication, and collaboration. Conclusion: The integration of SQD into science teachers’ online professional development programs will provide useful and productive outputs in terms of content, participation, communication, and collaboration.