The occurrence of building failure and collapse has become a major issue of concern in the development of this nation as the magnitudes of this incident are becoming very alarming. This paper therefore examines the incidents of building failure/collapse in Nigeria. By focusing on six major states from each of the six geo-political regions of the country, the paper examined the contributory role of the informal sector to this decadence. The study indicated that the building failure and collapse stem principally from hasty construction, low quality workmanship, poor supervision, inexperience (use of incompetent hands), ignorance, evasion/ non-compliance with building regulations and non enforcement of building quality, standard and control on construction site/market. This study has revealed that more than 70% of the reported cases of building collapse in Nigeria stemmed from the informal sector. It further showed that 70-0%, 23-3% and 6.7% of the reported cases occurred in private, public and corporate organizations respectively. In this paper, it is concluded that it is important to educate or giver further advice to the government and the governmental agencies to be proactive to their duties in order to curb/reduce this negative image.