Background: As one domain of preoperative assessment, Pre-operative investigations are often ordered to evaluate patient’s medical condition, for risk stratification and assessing patient status to undergoing surgery. Despite the fact that laboratory testing can assist ensure the best possible preoperative condition, routine screening examinations have a number of drawbacks. Although there are evidence-based recommendations for which investigations should be done, the tradition of routine preoperative testing is still prevalent and clinical practice with abnormal result detected varies. Method: Institution based cross-sectional study design was conducted from July1 to September 30 at Dilla University Referral Hospital. Data was collected from complete pre-anaesthesia check-up sheets, investigations already done. It was collected at the individual level by using, closed ended self-guided questionnaire. The collected data was entered, cleaned, edited and checked using SPSS version 26 for data processing and analysis. Logistic regression was performed to examine impacts of abnormal preoperative investigation result and summarized by using tables and figures. An Adjusted odds ratio with 95% confidence interval was computed to determine the level of significance. Result: Data of 208 patients (65.9 female) with mean±standard deviation age 30.83±15.340 years and 22.59±2.99 BMI were analysed. Patients were mostly American Society of Anaesthesiologists I and II underwent National Institute of Clinical and Health Excellence Grade 2 surgeries and surgical shape class 3. Totally, 178 (44.5%) test results were abnormal. CBC is the most detected abnormal result. Only 15(3.75%) abnormalities had an impact in terms of delay, further investigations, and surgical technique. Comorbidity (AOR 7.982, 95% CI, P-value=0.041), medication history (AOR 1.463, 95% CI, P=0.013), ASA physical status II (AOR3.287, 95% CI, P=0.029) and history of smoking (AOR 1.577, 95% CI, P-value=0.049) were factors which was significantly associated with abnormal preoperative investigation result Conclusion: Only 0.6% of all tests had a significant impact in terms of changing perioperative anesthetic management. Significant impact of abnormal investigation result noticed was delay surgery