Do liberals’ and conservatives’ brain processes differ in moral reasoning? This research explains these groups’ dissimilar moral stances when they face ethical transgressions in business. Research that explores the effects of ideological asymmetry on moral reasoning processes through moral foundations (i.e., fairness and authority) has been limited. We hypothesize two different moral reasoning processes and test them in the South Korean culture. Study 1 uses the neuroscientific method of event-related potentials (ERP) to explore the dissociable neural mechanisms that underlie Korean liberals’ and conservatives’ moral reasoning processes in business ethical transgressions. Liberals’ early frontal negative-going (EFN) brain waves showed that they are quick to pass negative judgment by intuitively detecting violations of fairness (i.e., moral engagement), while conservatives’ temporoparietal positive-going (TPP) brain waves showed that they have a higher motivation to respect authority (i.e., moral rationalization). Both liberals’ and conservatives’ ERP components occur within the first second of the decision-making phase, suggesting the rapid and intuitive nature of moral reasoning processes. Study 2 tests a mediating process and confirms that Korean liberals (conservatives) exhibit the moral engagement (rationalization) strategy, through the fairness (authority) foundation. These findings from our interdisciplinary research deepen the knowledge of the complexity of human morality in business ethics research.