The purpose of this study was to investigate in-service physical education teachers' engagement during online adapted physical education (APE) graduate professional development. This study was based on andragogy theory. All participants were in-service physical education teachers enrolled in a state-approved online APE endorsement program at a Midwestern public university in the United States. The program includes two online courses (Introduction of APE and Practicum in APE). Data collection included face-to-face open-ended interviews, peer-review feedback assignments, practicum experience reports and bulletin board discussion logs. As supplement material, this study used a demographic questionnaire which included questions pertaining to the participants' personal characteristics (e.g. race, age, sex) and current teaching experiences. A constant comparative method was used to interpret the data, and this allowed themes to emerge from the data as well as from the theoretical framework. Four interrelated themes emerged from the physical education teachers' narratives: interactions with online APE professor; peer interaction in online APE practicum courses; assessment practices with peers; and sharing through online discussion. This study recommends that online course instructors may consider changing their instructional style (pedagogical orientation) to problem-solving learning styles (andragogy orientation) that enhance teachers' engagement in online learning.