Mean platelet volume (MPV) is a reflection of platelet size, which has been shown to correlate with platelet function and activation. Infections as inflammatory process are known to be associated with change in PLT indices. The purpose of this study was to evaluate platelet indices especially MPV in acute pyelonephritis and their changes after response to treatment. Adult patients who were admitted with diagnosis of acute pyelonephritis were considered for participation in the study. Control group were selected randomly from healthy adult normal population whom underwent medical check-ups at the same hospital. Platelet indices values in patients and control subjects were measured on admission and 3 days after response to treatment in patients. A total of 60 patients with acute pyelonephritis and 60 healthy people as a control group were included in the study. MPV and Platelet distribution width (PDW) were significantly different between patients and control group (p=0.005). Platelet count in patients was higher than control group but the difference was not significant. Platelet count and PDW values decreased significantly after response to treatment (p<0.001 and p=0.007 respectively). MPV and PDW may be useful markers in acute pylonephritis and as an auxiliary test in the diagnosis. PDW and platelet count also may be considered markers of response to treatment for acute pyleonephritis.