Background: Teachers play a prominent role in facilitating the integration of engineering into school instruction. There is an extensive body of literature that has addressed the delivery of engineering teacher professional development programs. A few studies have summarized the features of engineering teacher professional development programs, but none have followed systematic synthesis procedures. Purpose: The study aimed to synthesize the literature on teacher professional development programs focused on the integration of engineering into K-12 education. The purpose of the study was to provide a systematic overview of the general characteristics and key features of PD programs. Design and Method: The systematic review involved three phases, search, selection, and synthesis, and included the application of exclusion criteria, inclusion criteria, and a checklist created by the investigators. Based on an extensive database and journal search, as well as the three review phases mentioned above, 29 articles previously published in peer-reviewed academic journals were included in this systematic review. Results: Results were organized according to six codes: (a) teacher profiles, (b) organizational features, (c) impacts of the professional development programs, (d) factors that promote professional development program effectiveness, (e) assessment of teacher improvement, and (f) addressed limitations. The majority of programs included face-to face workshops combined with field trips to engineering workplaces and follow-ups. Factors that contributed to the effectiveness of the programs included: real-world-focused activities, the promotion of collaboration and interaction with peers and outside experts, development and refinement of plans for classroom implementation, and observation of student interest and progress. Conclusions: This systematic review can provide a conceptual basis for research and practice in engineering-focused teacher professional development, with the assistance of research-based guidelines presented. Future research can investigate the possible long-term effects of the guidelines provided for teachers and their students.