This paper examines the application of the ethics of duty to the ethical issue of conflict of interest in public administration in Nigeria. Resolving conflicts of interest among public administrators is crucial to effective and efficient service delivery in the nationís public service. All the different forms of conflicts of interest have made the achievement of the statutory intentions of Ministries, Departments, and Agencies (MDAs) of government at all levels unachievable. Given this, the paper argues that unresolved conflicts of interest have several negative consequences such as: reducing public confidence and trust in government and public administrators, undermining stability and eroding trust in public institutions, affecting the level of effectiveness and efficiency of public service delivery, and affect the socio-economic development of the nation among others. The paper concludes that the inculcation of the prescription of the ethics of duty by public administrators will enable them to act under laws, codes of conduct, regulations, and ethics for the public good, this will, in turn, help public administrators to be ethical, effective, and efficient which ultimately brings about social, economic, and political development in the nation.