Objective: The Bridging the Gap Between Physical and Mental Illness in Community Pharmacy ("PharMIbridge") randomised controlled trial (RCT) aims to test the effectiveness of a pharmacist-led support service in improving medication adherence, and the physical and mental health of people living with severe and persistent mental illness compared to a standard medication review service. Method: Using the six-step intervention mapping (IM) framework, this paper describes the development and content of the "PharMIbridge" pharmacist training programme, an integral part of the RCT implementation, and continuous adaptations made to the process to keep pace with the evolving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in Australia. A Training Working Group comprising health educators, practitioners, mental health consumers and researchers, refined the programme objectives and assisted with developing content and troubleshooting issues related to training delivery for pharmacists randomised to the RCT intervention arm. Results: A 2-day training programme was developed, which included Mental Health First Aid, simulated patient role-plays, and four pre-recorded modules using lectures, demonstration case vignettes, role-play activities and discussion. The programme, co-facilitated by project team members and mentors (pharmacist and consumer educators), aims to enhance pharmacists' mental health literacy, skills and confidence and empower them to engage with this vulnerable population using a strengths-based approach. Pre- and post-training questionnaires and interviews will be used to evaluate the impact of the "PharMIbridge" training programme. Conclusion: The systematic stepwise method provided by the IM framework highlights the solution-focused approach adopted by the project team and characteristics including adaptability and resilience which enabled training development and implementation across four Australian regions during the SARS-CoV-2 pandemic.