Teenage pregnancy remains a significant global public health challenge with farreaching implications for adolescents, their families, and society at large. This study examined the major factors influencing teenage pregnancy among secondary school students in Alimosho Local Government Area of Lagos State, Nigeria. A cross-sectional descriptive research design was employed, involving two selected secondary schools in the area. The study sample comprised 220 students, and data were collected using a selfstructured questionnaire. Statistical analysis was conducted using the Statistical Package for the Social Sciences (SPSS). Out of the 220 respondents, 80 (36.4%) were male and 140 (63.6%) were female. Participants’ ages ranged from 13 to 21 years, with 78 (35.5%) aged 13–15 years, 136 (61.8%) aged 16–18 years, and 6 (2.7%) aged 19–21 years. Regarding religion, 102 (46.4%) were Christians, 114 (51.8%) were Muslims, and 2 (0.9%) identified as traditionalists. The study further revealed that 32 respondents (14.5%) had experienced teenage pregnancy. The findings underscore the key factors contributing to adolescent pregnancy among secondary school students in Alimosho Local Government Area. The study emphasizes the urgent need for the implementation of comprehensive sex education programs within schools and communities to curb the incidence of teenage pregnancy and mitigate its associated health and social consequences.