Since her independence in 1960 from the British colonial administration, Nigeria has remained a country with multi-ethnic, multi-religious and regional diversity. This composition rather than being a blessing has become a serious threat to National unity, peace and socio-economic development. This is because the Nigeria socio-economic and political landscape is characterised by tribalism, nepotism, ethnic rivalry, favoritism, corruption, inter-ethnic and religious conflicts, amongst others. The result is the mistrust and suspicion and intolerance among the various ethnic and religious groups in Nigeria thus, impeding the much-needed peace and development. This paper, therefore, assessed the ethno-religious conflicts as a bane of sustainable peace and development in Nigeria. It drew its data from the secondary documents while conflict theory was used in the analysis of the subject matter. The findings showed that ethno-religious conflicts stemmed from fear of exclusion, domination by majority groups, and unequal access to opportunities, intolerance, elites’ manipulation among others. These have led to loss of lives and property, thereby obstructing the peace and development in the country. Arising from this, the paper recommended an end to Elite manipulation of ethnicity and religion for personal aggrandizement; promotion of tolerance among citizens; and an inclusive government for the interest of the minorities.