Objectives Henoch-Schonlein Purpura (HSP) is the most common self-limiting vasculitis of childhood. Both serious gastrointestinal and renal complications may be observed during the disease course. The aim of this study was to evaluate the role of hematological markers in predicting the likely complications of the disease. Methods The demographic findings, clinical features, organ involvements and laboratory findings including white blood cell count (WBC), neutrophil, lymphocyte and platelet counts, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), mean platelet volumes (MPV), MPV/platelet count ratio (MPR) were evaluated retrospectively from the charts of the patients with HSP and all these parameters were compared with the same parameters of healthy children. Results A total of 376 patients with HSP and age- and sex-matched 233 healthy children were evaluated. Mean age at the diagnosis was 7.5 +/- 3.5. All patients had palpable purpura, 46% had arthritis, 56.1% GIS involvement and 21.3% had renal involvement. While platelet counts, neutrophil counts, NLR, and PLR were higher, lymphocyte counts, MPV, and MPR were lower in patients with GIS involvement. NLR was the sole biomarker that was higher in patients with renal involvement. Conclusions This study had shown that platelet counts, neutrophil counts, NLR, and PLR were increasing and lymphocyte counts, MPV, and MPR were decreasing when the patients had GIS involvement. However, these parameters were not relevant in distinguishing severe and mild GIS involvement. When patients had renal involvement NLR was the unique elevated parameter.