Background: Platelet count is important in assessing patient response after platelet transfusion. Despite their numerous side effects, platelet transfusions lack research on their appropriateness. In this study, the corrected count increment (CCI) 1 hr and 24 hr after platelet transfusion was measured to assess the appropriateness and therapeutic response to platelet transfusion according to blood transfusion guidelines. Methods: Platelet counts and individual characteristics were reviewed in platelet transfused samples for 9 months. A national transfusion guideline was used to determine platelet transfusion appropriateness in 384 samples, and the therapeutic response to platelet transfusion was evaluated according to CCI at 1 and 24 hr after transfusion in 374 samples, excluding 10 samples from patients who did not have height and weight records. Results: Platelet transfusions were performed 384 times with 2,729 units of platelet product. A total of 245 (63.8%) platelet transfusions were done under transfusion guidelines. CCI-1 hr and CCI-24 hr could be calculated in 31 (8.3%) and four (1.1%) of 374 samples, with the results of CCI-1 hr ≥ 7,500 and CCI-24 hr ≥ 4,500 in 17 of 31 cases (54.8%) and two of four cases (50.0%), respectively. Conclusions: It is important to evaluate the adequacy and effectiveness of transfusions using appropriate indicators. HLA-compatible platelet preparation might improve platelet transfusion effectiveness when immunological processes are the suspected causes of platelet incompatibility. Furthermore, since platelet transfusions vary by medical setting, evaluating the appropriateness and therapeutic effects of platelet transfusions at various points within a hospital could be helpful for patient blood management.