Introduction:Abnormal uterine bleeding (AUB) is one of the most common gynecologic complaints among reproductive-age womenwhich is one third of outpatient visits to the gynecologist are for AUB. symptom for the majority of women who undergo a hysterectomy which represents the most Abnormal uterine bleeding is one of common causes of anemia in women. AUB is the presenting common gynecological procedure in the world, has substantialsurgery related complications.The objective of this study is to assess the magnitude of AUB and its related factors among reproductive age woman. Methods:An institutional based cross-sectional study was conducted. Among 502 women who visit gynecologic OPD at two tertiary hospitals in Bahir Dar from March 1, to June 30, 2023. Study subjects were selected using systematic random sampling technique. Data was collected using interviewer administered pretested well structured questionnaire. The collected data were coded and analyzed using Statistical Package for the Social Sciences version 25(SPSS, 25). Bivariable and multivariable logistic regressions were fitted to assess the association between independent and the dependent variables. P-value less than 0.05 at 95 % CI was used to declare statistical significance association. The result was presented using texts tables. Result:Themagnitude of abnormal uterine bleeding was 33.3% (29.3-37.7, 95% CI). Having history of abortion (AOR= 3.95, 95%CI), woman currently use hormonal contraceptives (AOR=3.82, 95% CI), those mothers having currently treatment for STI (AOR=2.52, 95% CI), and alcohol consumption (AOR=4.01, 95%CI)had a statistical positive association with abnormal uterine bleeding. Conclusion: Prevalence of abnormal uterine bleeding is high. History of abortion, use of hormonal contraception, current treatment for STI, and alcohol intake were predictors for AUB. Recommendation:Health care providers in the tertiary hospitals should be vigilant in diagnosing AUB and importantly its possible causes and create awareness for patients to decrease risks of STI and prompt treatment for those having it. Public health personnel’s should create awareness in the community about AUB and its potential causes, on prevention of STI has multiple health benefits Key words:Abnormal uterine bleeding, tertiary hospitals, FelegeHiwot Hospital, TibebeGhion Hospital, cross-sectional study