This study examined the relationship between military professionalism and civil-military relations in Nigeria. Focusing on the period between 1960 and 2007, it explored the connection between understandings of professionalism amongst members of the armed forces and the way they relate to the rest of Nigerian society. Prolonged military rule (1966-1999) and the military’s heavy involvement in domestic security, resulted in increased militarization of Nigerian society and placed considerable strain on civil-military relations. The conduct of Nigerian military personnel in their dealings with civilians and their representatives faced criticism by members of the Nigerian civil society and the international community for being exploitative, heavy-handed and inconsistent with expected standards of military professionalism. Yet, during this period the military also increased its international profile, and came to be regarded, especially in the area of international peacekeeping, as a significant force within its region and beyond. Greater accountability and stricter adherence to professional standards were part of the democracy dividends expected by Nigerians when successful elections were held in 1999. Yet, two decades later, the relationship between the military sphere and the civilian sphere has been fractious and conflictual. This thesis considers that efforts to promote military professionalism need to engage with apparent and evidential understandings of military professionalism held amongst military personnel themselves. On this basis, the study has sought to introduce military voices into the discourse on military professionalism. The study adopted a mixed methods approach incorporating both qualitative and quantitative methods in gathering perspectives held by members of the Nigerian military and the civil population about military professionalism. It found that the military’s self-image, in terms of its professionalism and values, is markedly at odds with the way it is perceived by the civilian population many of whom see it as a highly politicised, unethical and coercive institution. Further, that the military identity is deeply complicated by pluralism, religious and ethnic diversity in Nigeria with specific consequences for its professionalism.