Unethical consumer behavior can cause serious damage to business and society. The concern is especially serious in Vietnam. This study examines the impacts of idealism, relativism, materialism, and self-monitoring (SM) on the ethical beliefs of Vietnamese consumers. We employ a multivariate approach to test the collective significance of each of those variables. More importantly, as opposed to previous studies, we account for second-order impacts of those characteristics to better capture the nature of the relationships with consumer ethics. Empirical analysis shows that idealism and materialism are major indicators for and have nonlinear impacts on the four dimensions of consumer ethics: actively benefiting from an illegal activity (ABIA), passively benefiting at the expense of others (PBEO), actively benefiting from a questionable action (ABQA), and no harm, no foul (NHNF). Relativism is not significantly related to consumer ethical beliefs. Self-monitoring did not have any impact or moderate the relationship between materialism and consumer ethical beliefs.