Background: Drug related problems (DRP) are common in hospitalized patients and may lead to increase hospital stay, health care cost and augment the risk of morbidity and mortality. Objective: The aim of this study was to assess the prevalence of DRP and associated factors among medical ward patients in University of Gondar teaching hospital (GUH) Methods: A hospital based prospective cross-sectional study was conducted on 256 patients who were admitted in the medical wards from February to April 2016. Data were collected using a pre-tested standard data abstraction format and semi-structured questionnaire. The collected data was checked for completeness and entered into Epi Info 7 software, and analysed using SPSS version 20. Descriptive, binary and multiple logistic regression analyses were used to assess the association between different variables. p<0.05 was used to declare association. Results: Of the 256 study participants, 169 (66.0%) of patients had DRP. A total of 174 DRPs were identified on average of 1.04 DRPs per patient. Of the identified DRP the most common DRPs were found to be due to inappropriate dosage 39.1 %, non-compliance 28.9%, and need additional therapy 24.2%. Length of hospital stay [adjusted odds ratio (AOR) =2.416 [95% confidence interval (CI) 1.111-5.253, p=0.028]), number of disease (AOR=3.315 [95%CI: 0.301-36.573], p=0.027) and number of drugs per patient (AOR=9.088 [1.012-81.623], p=0.033) significantly affect DRP. Conclusions: DRPs are common among medical ward patients in GUH. Inappropriate dosage and unnecessary drug therapy were the top and the least prevalent DRPs respectively. Early identification of DRP and the associated factors to them may enhance the prevention and management of DRPs.