Background: Unintended pregnancy is a mistimed, unplanned or unwanted pregnancy at the time of conception. Unintended pregnancy has a number of adverse physical, mental, and social impacts. It brings illegal and unsafe abortions which are causes of maternal morbidity and mortality in the developing countries like Ethiopia. Even if such problem has significant impact on the community, there is scarcity of evidence on this issue in Ethiopian higher institutions. Therefore, this study was aimed to assess unintended pregnancy and associated factors among unmarried female students in Bahir Dar University, North West Ethiopia. Methods: A descriptive, cross-sectional study was conducted among unmarried female students at Bahir Dar University from March 1 st -30 th , 2018. Data were collected by self-administered questionnaire. Data were entered, cleaned, coded and analyzed using SPSS version 23.0. The statistical association between dependent and independent variables was assessed using logistic regressions. P-value <0.05 in the multivariable analysis was set to statistically significant. Result: Three hundred eighty-nine students had participated in the study making the response rate 92.00%. The prevalence of unintended pregnancy was 10.00%. Getting money from family (AOR: 0.16, 95% CI: [0.06, 0.42], p < 0.001) and being Health Science student (AOR: 0.40, 95% CI [0.16, 0.98], p < 0.001) were the preventive factors of unintended pregnancy. Being age of less than or equals to 18 years in the first sexual intercourse time (AOR: 6.31, 95% CI: [2.56, 15.53], p < 0.001) was positively associated with unintended pregnancy. Conclusion:In the current study the prevalence of unintended pregnancy was high among unmarried female University students. Unintended pregnancy was determined by the source of money, field of study and age at first sexual intercourse. Hence, students should use family as a source of money, abstain from early sexual intercourse and share experiences from Health Science students about the prevention of unintended pregnancies. In line with the alleviation of modifiable factors, health professionals should provide comprehensive reproductive health and contraceptive services to University students.