Objective: To determine diagnostic accuracy of increased mean platelet volume as inflammatory marker in diagnosis of acute appendicitis taking histopathology as gold standard. Study Design: Cross Sectional Study. Setting: Department of Surgery, Abbasi Shaheed Hospital, Karachi. Duration: From 28th October 2016 To 27thApril 2017. Material and Methods: Total 229patients suffered from acute appendicitis were included. Venous blood (<20 ml) for complete blood count was sent to lab before surgery. MPV >11fl was taken as increased value. Post-appendicectomy appendix was sent for histopathology. Sensitivity, specificity, positive and negative predictive values were calculated. Stratification was done. Chi-square test was applied post stratification and p-value ≤0.05 was considered as significant. Results: There were 128 male and 101 female. Mean age was 34.09±6.63 years. Mean duration of symptoms was 28.97±11.89 hours. 107 patients were observed with total leukocyte count >10X103µL. Mean platelets volume was more than 11 fl in 47.2% patients. Sensitivity, Specificity, PPV, NPV and accuracy were 74.6%, 91.6%, 92.5%, 71.9%, and 81.6% respectively. Conclusion: In conclusion in patients with temporary diagnosis of acute appendicitis, high MPV “≥ 11fl” can assist in the identification of acute appendicitis hence negative rate of appendectomy can be decreased.. Keywords: Diagnostic Accuracy, Increased Mean Platelet Volume, Acute Appendicitis, Histopathology