On 22 May 2017, the Manchester Arena bombing resulted in twenty-two fatalities, marking the United Kingdom’s most lethal terrorist attack since 2005. A subsequent public inquiry revealed the necessity for improved operational, tactical and strategic response and management strategies, and highlighted the barriers to effective decision-making processes of those present during the incident. Integrating macro-level societal ideologies, meso-level group dynamics and micro-level individual factors to understand decision-making complexities and the challenges, the present study thematically evaluated decision making, providing fresh insights into the multifaceted nature of high-stakes decision making. Using twelve transcripts, with an applied data saturation approach, findings represented three primary themes across the macro, meso and micro dimensions. Combined, these findings highlighted gaps between theoretical concepts and training, and practical application in high-stakes situations. It also highlighted difficulties in immediate response action, command and control and balancing established protocols with the need for adaptability in unpredictable emergency situations. We conclude that response decisions should be driven by the desire to optimize least-worst outcomes.