In Nigeria, many urban centers sprung up as a result of colonial administrative development and its subsequent mining activities. A typical instance is the cities of Port Harcourt, Enugu and Kaduna which emerged as administrative, commercial or mining centers. Similarly, Onitsha, a budding traditional society, metamorphosed over time to be a commercial center in Eastern Nigeria. In lieu of this, the competition between migrant traders and indigenes intensified over land ownership and customary rights. In recent times, Onitsha faces the challenge of inadequate spaces both for its businesses and for its residential quarters resonating communal conflicts between neighbouring communities: a consequence of urbanization pressure developed during the process of land acquisition. Largely, this paper aims at investigating the inherent causes of rural-urban migration as well as exploring the contributions and challenges of migrants in Onitsha. Employing qualitative and quantitative methods of historical inquiry, this paper will attempt an analysis, using Onitsha as a case study, of differing problems and prospects of sustainable urban development in Nigeria. Three qualitative techniques namely: phenomenological approach, narrative approach and process tracing will be utilized for data collection, its analysis and in the interpretation of findings. The paper will mostly investigate the contradictions inherent in migration patterns and how these affect settler-indigene relations in the city of Onitsha, South-Eastern Nigeria. The push-pull theoretical paradigm by Ernest Ravenstein complemented by the individual/opportunity nexus theory advanced by Shane and Venkartaraman will be appropriated for this purpose. Basically, the crux of the study purports that Onitsha's urban development lies currently on a tinder box as the city's lack of an urban development plan has resulted in the emergence of illegal structures especially on water ways; a classic case being the River Niger which may one day overflow its banks thereby birthing detrimental consequences. Against this background, an efficient town planning committee instituted by the government should ensure adequately that Onitsha is restored to its prior status as a plush and plum city.