Background: Currently, irrational uses of medicines becoming global problem largely in developing countries like Ethiopia. Inappropriate prescribing is a major cause for poor treatment outcome and higher costs. Hence, this study was aimed to investigate medicine prescribing practice and prescription errors using WHO medicine-utilization core indicators. Methods: A hospital based retrospective cross sectional study design was used to evaluate prescribing practices and prescription errors from September to October, 2024 at the OPD pharmacy using systematic random sampling technique while a prospective approach was employed for facility indicators. Presence of potential drug-drug interactions (DDIs) were evaluated using Medscape Online Drug Interaction Checker. Data were analyzed using SPSS version 25 and interpreted as tables and figures. Results: A total of 1019 medicines were prescribed in 524 prescriptions and 81.6% (n = 832) were actually dispensed. The percentage of antibiotic, injections and medicine prescribed from Essential Drug List was 33.9% (n = 345),3.5% (n = 36) and 92.3% (n = 941) respectively. The most frequently prescribed class of medicine were antibiotics 33.9% (n = 345). 65.1% (n = 341) were ≥2 medicines and 8.3% (n = 85) had at least one potential DDIs. Among overall DDIs, the monitor closely and serious level was 60% (n = 51) and 11.8% (n = 10) respectively. The average prescription error was 4.3. Prescription errors due to failure to mention diagnosis was 40.6% (n = 213). Conclusion: Based on findings, the prescribing practices had defects to the optimum value recommended by WHO and showed high prescription errors. Antibiotics prescribing was the major problem in practice. Remarkable DDIs were observed in prescribed medicines. Therefore, designing and implementing policy to improve medicine use practice is highly indispensable.