This paper presents the findings of a study which examined the relationship between ethical leadership, organizational harmony, and two dimensions of employee voice behavior including employee promotive voice behavior and employee prohibitive voice behavior in the Vietnamese workplace. Further, the study determined the influence of ethical leadership, and organizational harmony on two dimensions of employee voice behavior. This articles also test the mediating role of organizational harmony in the relationship between ethical leadership and employee voice behavior. Although these interrelations are very important for enhancing employee voice behavior, few empirical studies analyze these relationship together. Besides, few empirical studies analyze these relationship in the Vietnamese context. Finally, the study examined the most important factor that influences employee voice behavior. This article explores those relationships using SEM with data from 687 employees in Vietnamese companies. The findings indicated that ethical leaders can foster organizational harmony that promotes employee promotive and prohibitive voice behavior. The analytical results also shown that organizational harmony plays a mediating role in the relationship between ethical leadership and employee promotive and prohibitive voice behavior. On the other hand, there is a positive association exists between organizational harmony and employee promotive and prohibitive voice behavior. Implications for future research, theory, and practice were discussed.