The purpose of this study was to examine the impact of a GenCyber camp curriculum on teachers' technology, pedagogy, and content knowledge (TPACK). The camp was designed to engage participants in developing the knowledge and skills to incorporate GenCyber Cybersecurity First Principles and GenCyber Cybersecurity Concepts (GenCyber, 2019) into their curriculums. Participants (37 middle and high school teachers from a variety of disciplines) attended one of two weeklong camps held at a Midwestern liberal arts university. Using the TPACK Self-Reflection and TPACK Self-Assessment Surveys, pre- and post-camp data were collected from participants. Findings indicate that participants demonstrated an increase in all domains of the TPACK framework from pre- to post-survey. The greatest increase was in Technological Pedagogy Knowledge (TPK) (0.57), followed by Pedagogical Content Knowledge (PCK) (0.51), and Technological Pedagogical Content Knowledge (TPACK) (0.46). GenCyber participants also demonstrated an average increase in pre- and post-test scores in all areas on the TPACK Self-Assessment Survey Results; however, individual results were mixed. The majority of participants (n=21), sixty percent, saw an increase in composite score from pre- to post, whereas 12 participants' (34%) scores decreased from pre- to post, and two (6%) stayed the same. Findings indicate the GenCyber Camp provided in-service teachers with the knowledge and skills necessary to incorporate GenCyber Principles and Cybersecurity Concepts into their curriculum. Recommendations for teacher professional development on cybersecurity are made.