Conference preparation (CP) is critical to interpreting quality, yet the decision-making process remains underexplored. This Critical Decision Audit (CDA) study examined expert interpreters’ CP decisions using the Naturalistic Decision Making (NDM) paradigm. Twelve expert Mandarin-English interpreters documented CP events through diaries, from which eight main decision points were identified. Analysis revealed 54 distinct cues and strategies that experts employed during CP and 26 expert-novice differences as perceived and recalled by the expert participants, many previously undocumented in interpreting literature. The findings expand existing knowledge of CP by illuminating cognitive aspects of expertise, offering insights for practitioners and trainers. This study bridges NDM and interpreting research, contributing a cognitive perspective to CP understanding.