Quality improvement of malaria services aims to ensure that more patients receive accurate diagnosis, appropriate treatment, and referral. The Outreach Training and Supportive Supervision Plus (OTSS+) approach seeks to improve health facility readiness and provider competency through onsite supportive supervision, troubleshooting, and on-the-job training. As part of a multicomponent evaluation, qualitative research was conducted to understand the value of the OTSS+ approach for malaria quality improvement. Semistructured key informant interviews, focus group discussions, and structured health facility-based interviews were used to gather stakeholder perspectives at subnational, national, and global levels. Data were collected globally and in 11 countries implementing OTSS+; in-depth data collection was done in four: Cameroon, Ghana, Niger, and Zambia. Study sites and participants were selected purposively. Verbatim transcripts were analyzed thematically, following the Framework approach. A total of 262 participants were included in the analysis; 98 (37.4%) were supervisees, 99 (37.8%) were supervisors, and 65 (24.8%) were other stakeholders. The OTSS+ approach was perceived to improve provider knowledge and skills in malaria service delivery and to improve data and supply management indirectly. Improvements were attributed to a combination of factors. Participants valued the relevance, adaptation, and digitization of supervision checklists; the quality and amount of contact with problem-solving supervisors; and the joint identification of problems and solutions, and development of action plans. Opportunities for improvement were digitized checklist refinement, assurance of a sufficient pool of supervisors, prioritization of health facilities, action plan dissemination and follow-up, and data review and use. The OTSS+ approach was perceived to be a useful quality improvement approach for malaria services.