Mental Health and Psychosocial Support (MHPSS) practitioners working in humanitarian contexts are at significant risk of mental health conditions, ultimately hindering the quality and sustainability of their work. Supportive supervision has shown to be effective in improving the wellbeing of MHPSS staff and volunteers and enhancing the effectiveness of MHPSS service delivery. Despite these proven benefits, there is a lack of standardised guidelines to inform supportive supervision within humanitarian contexts. To address this gap, the Trinity Centre for Global Health and the International Federation of the Red Cross Red Crescent Societies’ Reference Centre for Psychocosial Support co-developed the ‘Integrated Model for Supervision’ (IMS) Handbook and supporting tools and led IMS trainings with four humanitarian organisations in Ukraine, Afghanistan, Jordan, and Nigeria from June-August 2021. The subsequent acute humanitarian emergencies that occurred in Afghanistan and Ukraine provided the opportunity to (i) examine the implementation of the IMS in the acute stages of two humanitarian crises and (ii) identify the challenges and lessons learned from this process. This study employed a case study design using semi-structured qualitative interviews with five MHPSS personnel (female: 4; male: 1) who had received training in the IMS and were directly involved in the implementation of supportive supervision using IMS guidelines in either Ukraine or Afghanistan. Results showed that participants identified the key steps needed for the implementation of supportive supervision and reported two significant barriers to implementation including the stress of a humanitarian crisis leading to competing responsibilities and priorities, staff shortages and time constraints as well as the challenge of creating a new supervision structure when none had existed previously. Overall, participants felt that the IMS resulted in improved knowledge, confidence, perceived support, team cohesion, staff wellbeing and was a helpful blueprint to guide the implementation of supportive supervision in humanitarian contexts.