Unintended Pregnancy is generally considered to be a high-risk event amongst adolescents due to various factors. Understanding factors predicting unintended pregnancies among in-school female adolescents can provide mechanisms for preventing unintended pregnancies and also providing youth friendly centers. In Nigeria, as a whole, unintended pregnancy among adolescents is a daunting problem. Studies have shown the prevalence of unintended pregnancy among adolescents to be 23% in the west, 36% in the southwest and 26% in the North central part of the country. It also ranges from 17% in Edo state and 6.2% in the other Niger Delta states to 49% in Abia State. The main Objective of this study is to investigate the Environmental factors predicting unintended pregnancies among in-school female adolescents in South-South Nigeria. A cross-sectional study which employed the use of quantitative methods of data collection was conducted among 239 in-school female adolescents who were selected through simple random sampling. Data was collected using a semi-structured validated questionnaire with Cronbach’s Alpha that ranged from 0.705 to 0.811. Data were analysed using descriptive and inferential statistics (logistic regression, correlation and chi-square). The result showed that those with low peer influence as compared with high peer influence were 0.92 times less likely to have unintended pregnancy (Odds ratio; 0.92; CI: 0.78-1.08; p=0.27). Low media influence as compared with those with high media influence had an odds of 1.01 likelihood of unintended pregnancy (Odds ratio=1.01; CI: 0.87-1.17;p=0.007), those with low parent support as compared with those with high parent support were 0.96 times less likely to have unintended pregnancy (Odds ratio=0.96; CI: 0.81-1.14, p=0.66). The environmental factor predictor was media influence while peer influence and parents’ support were not good environmental predictors of unintended pregnancy. Re-engineering media sources are needed to produce more positive and protective behaviours towards adolescent sexuality.