Introduction: Unwanted fertility is a serious problem in achieving a stable population in India particularly in backward regions. Aim: The study is to examine the determinants of unwanted fertility in tribal-dominated valley areas of Manipur, Indian easternmost state internationally bordering Myanmar. Materials and Methods: A cross-sectional study of 1152 currently married women of age below 52 years was conducted under a cluster sampling scheme from May 2018 to April 2019. Logistic regression along with classical t __ampersandsignndash; statistics explores the risk factors of unwanted fertility. Result: The fertility of tribal women (3.1) is significantly higher (P__ampersandsignlt;0.01) than non-tribal (2.6). Low education (P__ampersandsignlt;0.01), sex of 2nd birth (P__ampersandsignlt;0.05) and son preference (P__ampersandsignlt;0.01) have been detected to be major causes of unwanted births. Conclusion: To save and control unwanted human births in backward regions of Manipur, son preference is needed to be elimi nated and also the education of couples may be enhanced.