Aim: To evaluate and identify pre-analytical, analytical and post analytical laboratory errors occurring in Pathology and Biochemistry Laboratories of a tertiary care teaching hospital. Study Design:An observational study was conducted on 287165 blood samples received in Central Laboratory for various laboratory investigations. Out of the 287165 samples, 200407 were OPD samples and 86758 were IPD samples. The study was conducted for a period of 06 months from August 2022 to January 2023. Methodology: All requisition forms, specimens, entered reports and certified reports were scrutinized, and any error identified was recorded according to the type of error. Root cause analysis was then performed for each error. Data was then analyzed for frequency distribution and Chi Square test applied for categorical variables. Strategies were then developed to prevent errors in different phases in various sections. Results: All data collected was compiled on Microsoft Excel worksheets. Statistical evaluation was done using simple percentage distribution. Data was analyzed using (SPSS) 23. Chi-square test was applied to compare categorical data. P<0.05 will be considered statistically significant. It was observed that error was detected in 0.46 % of samples of which 0.2 % were OPD Samples and 0.01 % were IPD samples. In 0.47 % cases pre-analytical errors, in 0.02 % analytical errors and 0.01 % post-analytical errors were observed. Conclusion: Errors in pathology and biochemistry investigations are the biggest limitation to laboratory services with impact on healthcare management and its cost. Majority of reasons involved behind these errors is within the scope of laboratory and thus can be reduced to a great extent