The commercial built environment accounts for considerable energy consumption and carbon emissions across Europe, making it a critical focus for achieving climate action goals. Retrofitting existing building stocks plays a crucial role in supporting the climate action goals in the region. Despite available policies and efforts to promote energy-efficient practices, small and medium enterprises (SMEs) are still lagging in implementing retrofitting measures. In Ireland, SMEs dominate the commercial built sector but face unique challenges that hinder their interest in retrofitting. This shows a clear gap between what is expected in policies and action plans, and what is actual implementation on the ground. To better understand how to bring SMEs to the retrofitting journey it is significant to understand behavioural drivers that trigger decision-making on energy efficiency retrofitting. This study employs a multi-method analysis that covers surveys, workshops, and interviews with SMEs on the decision-making processes related to energy efficiency retrofitting actions within SMEs. Findings from the study reveal that drivers such as perceived financial benefits, environmental values, regulatory awareness, and organisational culture significantly impact decision-making processes. The findings underscore the need for tailored communication strategies and targeted support mechanisms to accelerate energy-efficient retrofitting in Irish SMEs. This research offers insights for policymakers and stakeholders aiming to foster sustainable practices within commercial buildings.