Background: Decarbonisation refers to the process by which countries, individuals or other entities aim to achieve zero fossil carbon emissions through reduction of greenhouse gas (GHG) emissions, including procurement, energy and buildings, pharmaceuticals, transport, and waste which impacts public health. Preliminary findings on decarbonisation in healthcare systems suggest that further research is required. Aims: This research was undertaken to explore the opportunities and barriers of decarbonisation of public hospitals within the ‘climate health’ planetary health boundary in the Republic of Ireland. Methodology: A literature review was used in conjunction with semi-structured qualitative interviews to explore barriers and opportunities of decarbonisation of Irish healthcare sector. The purposive sampling for the qualitative interviews resulted in the selection of five key decision-makers within cross-sector fields including environmental, public health, management and transport. Results: Themes emerged which reflected the cross-cutting planetary health principle. Barriers such as financial incentives and the requirement for a transdisciplinary approach were raised. The need for preparing the healthcare sector through adaptation and mitigation of the effects of climate change was also highlighted, as was the importance of leadership within the hospital from all sectors. Recommendations: The findings emerging from this novel research through a planetary health lens can be used to further inform the ‘Climate Action Plan’ in the Republic of Ireland, with adaption to other healthcare sectors internationally, in order to ensure investment within the health sector in preparation for climate change.