Objective: Monocyte to HDL cholesterol ratio (MHR), lymphocyte to monocyte ratio (LMR) and neutrophil to lymphocyte ratio (NLR) have been proposed as novel systemic inflammatory markers. The aim of this study was to explore the association between MHR, LMR, NLR and pulmonary arterial hypertension (PAH). Methods: The study is a single-centre, retrospective observational study. The study group consisted of 73 patients with PAH and the control group consisted of 77 participants without cardiac pathology as determined by echocardiography. On admission, blood sampling to calculate MHR, LMR, NLR and detailed clinical data were obtained. Results: According to the Pearson test, systolic pulmonary artery pressure (PAP) value positively correlated with the MHR and NLR (r: .35, p<0.001 and r: .33, p<0.001, respectively), but negatively correlated with LMR (r: -.26, p=0.001). After multivariate logistic regression analysis, MHR, LMR and NLR remained a significant predictor of PAH (OR: 2.972, 95% CI: 1.541-5.731, p=0.001; OR: 0.515, 95% CI: 0.385-0.687, p<0.001; OR: 1.390, 95% CI: 1.083- 1.784 p=0.010, respectively). Conclusion: Higher MHR, NLR and lower LMR that indicates an enhanced inflammation were significantly increased in patients with PAH compared with controls. Compared to many other inflammatory markers, these markers are cost effective, widely available and does not bring additional costs. Keywords: Pulmonary arterial hypertension, Monocyte to HDL cholesterol ratio, lymphocyte to monocyte ratio What’s already known about this topic? MHR, LMR and NLR have been proposed as novel systemic inflammatory markers in clinical studies. What does this article add? The association between MHR, NLR and LMR with PAH is unknown. In this study these parameters were significantly associated with PAH. Compared to many other inflammatory markers, these markers are cost effective and widely available.