This qualitative study aimed to describe the collaborative process followed by an in-service teacher and two university researchers in co-designing and implementing a Health-based Physical Education/Sport Education hybridization and to explore the perceived strengths/weaknesses of the process. An 11-lesson (six weeks) intervention on rope-skipping was conducted in a 5th-grade classroom. Qualitative data was collected (teacher's interviews, participant observation and video recording) and analysed using a multiphase approach combining inductive and deductive (based on models features and intervention's pedagogical principles) thematic content analysis and constant comparison. Self-reflective cycles were applied to reinforce the teaching-learning process by sharing professional knowledge and reflections. Results revealed that the collaboration with researchers helped the teacher to check whether it was consistent with the models' goals and critical elements and readjust her practice. The teacher was crucial to the co-design and adaptation of the hybridized models to the local context due to her knowledge of the school and pupils. From the collaborative team's perspective, her role during the implementation fostered group co-responsibility, respect for students' different motor competencies, and transference of practice beyond the school timetable. This contributed to encouraging students' physical activity involvement in an informed and autonomous way. However, a longer initial 'Guidance stage' was deemed essential to help students learn basic concepts and skills to better progress in an informed and self-managed way. Longer interventions and research are necessary to delve deeper into the understanding of pedagogical models. A collaborative approach may help teachers to face initial involvement in the pedagogical models' implementation.