ObjectiveThe study was aimed at determining the prevalence of unintended pregnancy and associated factors in Arsi Negele Woreda from May 01, 2017 to July 30, 2017.ResultsUnintended pregnancy was found to be 41.5%. The multivariable logistic regression revealed that 35 and above age group (AOR; 2.343, 95% CI 1.374, 3.997), single marital status (AOR; 6.492, 95% CI 1.299, 32.455), parity of 2 (AOR; 53.419, 95% CI 21.453, 133.014), parity of 3 and above (AOR; 20.219, 95% CI 7.915, 51.655), having abortion history (AOR; 1.962, 95% CI 1.025, 3.755), having health professional visit (AOR; 2.004, 95% CI 1.218, 3.298) and having autonomy to use contraceptive method (AOR; 2.925, 95% CI 1.648, 5.190) were significantly associated with unintended pregnancy. Therefore, reproductive health advocacy, counseling and access of modern contraceptive methods are recommended.Electronic supplementary materialThe online version of this article (10.1186/s13104-018-3778-7) contains supplementary material, which is available to authorized users.