Psoriasis is a chronic inflammatory, immune-mediated disease, and platelets have an important role in the pathomechanisms of psoriasis. Recent studies showed that MPV (mean platelet volume) could be used as a marker of platelet activation. In this study, we aimed to investigate the MPV level and platelet count in psoriasis patients and its association with disease severity.We designed a case-control study with 28 psoriasis patients and age and sex-matched 30 healthy controls. Haematologic parameters and sedimentation rates compared between groups. These parameters also correlated with PASI (Psoriasis Area and Severity Index) score.MPV and platelet count were significantly higher in patients with psoriasis than controls (p=0.012, p=0.015). Also, platelet count was showed positive correlation with PASI scores (r=0.424, p=0.025). The sedimentation rate was not statistically different between groups.There are many conflicting results about the correlation of haematologic parameters and psoriasis. We found that MPV and platelet counts higher in the psoriasis group, which suggests that platelets play an important role in the pathomechanism of psoriasis and may be helpful in assessing treatment outcomes.