Under a presidential system of government, executive powers are vested on the President at the federal level and the Governor at the state or sub-national level. Given the wide powers constitutionally conferred on the executive arm of government along with immunity from civil or criminal proceedings, the instrument of impeachment is incorporated into the Constitution to act as a check and balance against authoritarianism or misuse of official power. The foremost objective of this article is to comparatively scrutinise the modus operandi for impeachment of the President or Governor in Nigeria and the United States of America (USA); the USA impeachment mechanism would be limited to the federal impeachment process of the President and the Vice President. The article employed desk-based or doctrinal and comparative research methods by placing reliance on both primary and secondary sources of information. The sources of information were analysed and inferences obtained were presented descriptively. The article revealed inter alia, that though Nigeria and USA practice presidential system of government as well as operate a federal system, yet, there are some procedural parallels and dissimilarities in their respective impeachment procedures. A case in point is that in the USA, an impeached official cannot subsequently be granted pardon by the President whereas in Nigeria, there is no constitutional clause barring the President or the Governor from granting pardon to a convicted elected executive office holder. The authors therefore, recommended inter alia, that a constitutional amendment should be introduced to sections 175 and 212 of the 1999 Constitution of the Federal Republic of Nigeria (1999 CFRN) with the goal of outlawing the President or Governor from granting pardon to an impeached official, as obtainable in the USA.