Acute appendicitis is currently the most common cause of emergency surgical interventions and it is important to form an early diagnosis. The mean platelet volume (MPV), which is a marker that reflects the dimensions and activation of platelets, has been shown to be a parameter in inflammatory responses, reflecting the activity of the disease in conditions. This retrospective study aims to define the values of MPV in acute appendicitis compared with the MPVs of a control group selected from among individuals with no inflammatory process. Patients who had undergone emergency surgery having been diagnosed with acute appendicitis between January 2008 and January 2015 were retrospectively evaluated. The control group consisted of patients who had presented to the General Surgery Clinic with a diagnosis of inguinal hernia, pilonidal sinus, nodular goitre and soft tissue mass (lipoma) at the extremities and who were planned to undergo elective surgery. Patients in the control group were defined as Group 1. The study groups planned as Group 2: Acute (non-complicated) appendicitis; Group 3: Complicated (presence of an abscess and/or appendiceal erforation); Group 4: Normal appendix (negative laparotomy). Once the data from all the groups had been obtained, cross comparisons were made between the groups in terms of age, gender, WBC level, and mean MPV, and the results were then statistically evaluated. In total, 1.790 patients were enrolled in this study. The mean MPVs in Groups 1 and 4 were very close, they were significantly higher than the values in Groups 2 and 3 (p < 0.05). In the comparison of Groups 2 and 3, while the mean MPV in Group 2 was found to be lower than the value in Groups 1 and 4 (p < 0.05), no overall significant difference was determined between Groups 2 and 3 (p = 0.11). MPV is a marker that is evaluated during routine hemograms (CBC). It incurs no additional cost and defines the platelet functions and activation. An increase in MPV can be used as a marker of increased platelet activation secondary to inflammation in the chronic phase. These results demonstrate that the MPV might be useful for, and significant in, diagnosing acute appendicitis. However, MPV is not significant in defining groups with and without perforation.