Implementation of mindfulness programs in secondary schools has increased dramatically in the past decade. Evaluations of these programs have primarily emphasized outcomes of participation, with less focus on implementation processes. Both are important to establish the initial evidence base and support dissemination and replication. The present study qualitatively explored factors that supported the initial implementation of a mindfulness-based martial arts intervention delivered in a secondary school setting for youth with or at risk for self-regulation challenges. Post-intervention, semi-structured interviews with 24 students (M[subscript age] = 14.87 years) and 2 group leaders, and focus groups with 10 teachers were completed to elicit their perceptions of factors that facilitated or hindered the implementation process. Exploratory thematic analysis suggested that factors differed by type of respondent but generally focused on three broad areas: fidelity to program characteristics, program delivery, and communication. Recommendations for secondary school-based implementation teams are discussed, in addition to future directions for mindfulness implementation research in secondary schools.