Supportive supervision is an important element of community health worker (CHW) programmes and is believed to improve CHW motivation and performance. A group supervision intervention, which included training and mentorship of supervisors, was implemented in Ethiopia, Kenya, Malawi and Mozambique. In three of the countries, this was combined with individual and/or peer supervision. A mixed-methods implementation study was conducted to assess the effect of the supervision intervention on CHWs' perceptions of supervision and CHW motivation-related outcomes. In total, 153 in-depth interviews were conducted with CHWs, their supervisors and managers. In addition, questionnaires assessing perceived supervision and motivation-related outcomes (organizational and community commitment, job satisfaction and conscientiousness) were administered to a total of 278 CHWs pre- and post-intervention, and again after 1 year. Interview transcripts were thematically analysed using a coding framework. Changes in perceived supervision and motivation-related outcomes were assessed using Friedman's ANOVA and post hoc Wilcoxon signed-rank tests. Interview participants reported that the supervision intervention improved CHW motivation. In contrast, the quantitative survey found no significant changes for measures of perceived supervision and inconsistent changes in motivation-related outcomes. With regard to the process of supervision, the problem-solving focus, the sense of joint responsibilities and team work, cross-learning and skill sharing, as well as the facilitating and coaching role of the supervisor, were valued. The empowerment and participation of supervisees in decision making also emerged in the analysis, albeit to a lesser extent. Although qualitative and quantitative findings differed, which could be related to the slightly different focus of methods used and a 'ceiling effect' limiting the detection of observable differences from the survey, the study suggests that there is potential for integrating supportive group supervision models in CHW programmes. A combination of group with individual or peer supervision, preferably accompanied with methods that assess CHW performance and corresponding feedback systems, could yield improved motivation and performance.