This study surveys the issue of military coups in Nigerian politics. An attempt is made to explain the causes of coups d'etat. To this end, Thompson's thesis of military grievances has been rigorously employed to explain the occurrences of military coups in Nigeria. The Thompson thesis asserts that coups occur because the military is aggrieved. A study of the opinions of expert observers familiar with Nigerian politics confirmed that four out of the six military coups occurred due to problems emanating from the Nigerian military establishment. Although military grievances such as its political positions, resource bases, ethnicity, and factions within the military caused most coups, there is sufficient evidence that societal factors like economic crises, election decisions, and the need for reforms also encouraged the military to overthrow governments in Nigeria.