Objective: An elevated level of NLR level is defined as an indicator of systemic inflammation, and it is stated that it can be used as an effective tool in navigating psychosis. The aim of the present study is to explore the blood parameters such as neutrophil, lymphocyte, and monocyte and their ratios (NLR, MLR, PLR) in both affective and non-affective psychosis. Materials and Methods: This is a retrospective case-control study conducted on schizophrenia(Sch), first-episode psychosis(FEP), and bipolar disorder(BD). Digital medical records were retrospectively analyzed between 2016 to 2021. The total number of patients recruited for this study is 437. Patients were divided into 3 groups which are schizophrenia (n:199), FEP (n:127), and Bipolar Disorder (n:111). The healthy control (HC) group (n:200) was selected who had never been diagnosed with any psychiatric disorders. Results: In this study, no difference was found between the patient groups in terms of substance use (Chi-square= 5.008; p= 0.082), platelet count was lower in SCH patients and no difference was found between the other groups in terms of platelet count. There was no statistical difference between the study groups in terms of lymphocyte, neutrophil, and monocyte counts and their ratios (NLR, MLR, PLR) (p>0.05 for each). Conclusion: In contrast to the previous findings, we did not show any significant differences in NLR, MLR, and PLR levels in both affective and non-affective psychosis. To better understand the pathophysiology of psychosis, it might be more suitable to conduct a clinical trial with drug-naive FEP patients in a prospective manner.