As an institutionalised mechanism, the presidential system prides itself as an accountability mechanism, for promoting good governance through decentralised oversight. As a governing system characterised by the axiom of separated but shared powers, presidential systems provide multiple opportunities to checkmate abuse of state powers. Thus, the institutional arrangement associated with its practice is designed to ensure prudent management of the state’s resources that enforce accountable leadership. In Nigeria, adopting a presidential system was a fallout of the failure of the First Republic Westminster parliamentary system, characterised by conflict and political instability. Nevertheless, the institutions associated with the system were not insulated from the attitudinal dispositions of political and bureaucratic leaders who often compromised statutory regulations in public sector management. Thus, disregard for the rule of law has remained the bane of the practice of the presidential system in Nigeria. This chapter discusses the institutions of the presidential system in Nigeria’s democratic experience. While explicit constitutional provisions stipulate the exercise of power with requisite accountability guides, members of the legislature, executive, and judicial arms of government have consistently breached the rules to circumvent statutory regulation of the functional accountability system. Consequently, institutional malfunctions are to the detriment of good governance. Compromised oversight institutions and mechanisms have failed to harness the requisite accountability potential for good governance.