Abstract—This study examined insecurity as the critical issue bordering the hearts of millions of Nigerians today, because all efforts by security agencies to combat the spate of unrest, like kidnapping for ransom, bombing, and assassination of innocent people, seem to yield no positive result. The study adopted a descriptive survey research design that was guided by three research questions. The respondents for the study comprised two hundred (200) knowledgeable people/youth selected from the Iseyin Federal constituency area of Oke-Ogun, Oyo state. The questionnaire titled Insecurity as a Major Threat to Human Wellbeing and National Development in Nigeria was the instrument used for the study. Descriptive statistics, such as frequency counts and percentages, were used to analyze the data collected. The study revealed that porous borders, unemployment, corruption, bad governance, and poverty are some of the factors responsible for insecurity in Nigeria. Poor standard of living, displacement of people, dislocation of family and communal life, and disruption of economic activities are among the impacts of insecurity on Nigerians’ social life and national development. It is recommended that the government should invest in job creation, restructure the security architecture of the country, and ensure social security programmes are pursued and systematically implemented towards meeting basic needs of the populace.