The nexus of the intractable corrupt practices in Nigeria and the proliferation of unconventional transnational organised crimes cannot be overemphasized. This has significant consequences for the socio-economic and sustainable development of the country. This chapter adopts social constructivism as its epistemological framework, and uses the broken window, rational choice, and social learning theories as its theoretical frame of arguments. The qualitative methods of content analysis and Key Informants Interview are used for the data collection and analysis. In this chapter, the author refers to content analysis as Open-Source Intelligence (OSINT) and the Key Informants Interview as Human Intelligence (HUMINT) for the security and intelligence audience. The chapter showcases the various forms of unconventional organised crimes in Nigeria and how these crimes are proportionally and inversely correlated to the intractability of corrupt practices among the elites in the country. For action, the author concludes and recommends that the international security agencies should collaborate with the Nigerian security agencies to fight these transnational organised crimes; and urges the International Monetary Fund (IMF) and the World Bank to stop giving shark loans to Nigeria based on its mineral resources and extractive industries because these loans are precursors to institutionalized corrupt practices.