Background: Stigmatisation and discrimination towards people with mental health problems in low- and middle-income countries (LMICs) is pervasive. Health professionals working in mental health services can play a critical role in stigma reduction. This study examines the feasibility, costs, and potential effectiveness of READ-MH for such professionals in LMICs. Methods: This multisite, nonrandomized pre–post mixed-methods feasibility study was conducted across all seven INDIGO-Partnership program sites. The impact of READ-MH was assessed pre and immediately post training and at three months follow up on: knowledge of training content; attitudes to addressing stigma as a professional; and clinical skills pre and immediately post training using an Objective Structured Clinical Examination (OSCE) with a scenario concerning anticipated stigma. Qualitative interviews of trainees at three months explored the impact on their practice. Results: Improvements in knowledge, attitudes, and clinical skills were reported. Mean knowledge scores increased immediately after training (+1.63; 95% CI 1.08–2.18) and were sustained at three months (+1.21; 95% CI 0.66–1.76). Increases were observed in the two attitudinal subscales i.e. role security (+1.28, 95% CI 0.82 to 1.74) and therapeutic commitment (+1.95, 95% CI 1.23 to 2.68) post-intervention, sustained at three months (+0.89, 95% CI 0.43 to 1.35) and +1.81; 95% CI 1.08 to 2.54). OSCEs total scores increased by 2.41 (+2.41, 95% CI 1.87–2.94). Qualitative data highlighted the training's relevance, advocacy orientation, and the importance of the experts by experience. Conclusion: Findings across multiple LMIC contexts demonstrate feasibility, cultural adaptability, and sustained impact, supporting further evaluation of READ-MH.