This work centered on Critical Discourse Analysis of Selected Inaugural Speeches of Nigerian Civilian and Military Heads of State. Critical Discourse Analysis is an indispensable tool in exploring opaque language uses that are assumed by writers as part of the background knowledge (Fairclough, 1985) and how the opacity of relations between discourse and society is itself a factor in securing power and hegemony (Fairclough, 1995; van Dijk, 2009). The practice of CDA in unravelling the opacity is also done critically by looking at the composite of the linguistic elements in the data.The study,therefore, is aimed at analysing the inaugural speeches of the Nigerian civilian and military Heads of State using Critical Discourse Analysis (CDA) with a view todetermining the pattern of the speeches of the Military and Civilian Heads of State; identify how the speeches convey the feelings/emotion of the Military and Civilian Heads of State; gauge the ideological inklings of the speakers in the speeches;establish how power is manifested in the speeches; measure how hidden meanings relate to social structure and identities of the Civilian and Military Headsof State in the speeches. Reviews of empirical and conceptual studies related to Critical Discourse Analysis (CDA) were conducted. The study adapted van Dijk (1993), Wodak (2001) and Fairclough (1989) as theoretical framework. In that regard, the research used Franklin (2000) method of essay structural layout,Johnson-Liard and Oatley's (1989) method of classification of language of emotion, van Dijk (1996) classification of ideology, Ng and Bradac's (1993) method of classification of power relations, Samovar et al (2007) classification of identityin analysing the data. On the structural pattern of the speeches, the Civilian Presidents were found to express gratitude using words denoting honour and elation to God and to the citizens through greetings. The speeches contained paragraphs that are narrative, expository, persuasive and promissory. The sentence types used included compound, complex and compound-complex sentences. In respect of the Military, the research showed that the Military Heads of State started also with greetings but entailing nerve racking and emotionally touching words and expressions. Their sentence types included compound, complex and compound-complex sentences. The tones they expressed were accusatory, abhorrence and gimmickry. The Civilian Presidents used Positive Basic Emotion and Positive Caused Emotion Expressions in their inaugural speeches. While the military used Negative Emotional Relations and Causative and Emotions Expressions in their speeches. Also, the research found out that Civilian Presidents expressed ideological beliefs of unity in diversity, fight against corruption and indiscipline and nation building. While the military expressed ideological beliefs of nation building and negative-other-presentation, the civilian presidents were found to express Positive-self Presentation, persuasion through personality and stance, persuasion through reasoning, persuasion through arousal of emotion, implicit threat and appeal as show of power in their speeches. While the military Heads of State expressed Positive-self Presentation, persuasion through reasoning, explicit threat and appeal as a mark of power. In relation to hidden meaning relating to social structure and identity of the speakers, the Civilian Presidents employed personification, irony, ellipsis, vague statements, deceptive statement, false promises etc. While the Military portrayed hidden meanings through negative-other presentation, hyperbole, euphemism, metonymy, adjective, conditional clauses, passivisation etc. in their inaugural speeches.The research recommends that the speeches should be appropriately documented and be subjected to linguistic analysis. More methods in Critical Discourse Analysis should be employed to conspicuously clear the opacity in the inaugural speeches. The inaugural speeches should be made constitutional because of the significance Nigerians attach to it.