Rationale, aims, and objectives: Raynaud phenomenon (RP) is a multifactorial disorder. If any underlying disease cannot be detected responsible for RP then it considered as primary RP (pRP). We aimed to investigate the differences between laboratory markers and impaired endothelial function in pRP. Method: Forty-two pRP patients included as study and control groups were created from 30 healthy individuals. The endothelial function was evaluated with flow-mediated dilatation (FMD) of the brachial artery. The blood samples were obtained both groups and white blood cell [WBC], hemoglobin, platelet, mean platelet volume [MPV], creatinine, alanine aminotransferase [ALT], aspartate aminotransferase[AST], D-dimer, fibrinogen, albumin, fibrinogen to albumin ratio [FAR], Neutrophil to Lymphocyte ratio [NLR], D-dimer to albumin ratio [DDAR] and monocyte chemo-attractant protein-1 [MCP-1]. Obtained blood parameters and FMD values were compared between groups. Findings: The groups were found as similar in regards to age, gender, smoking history (p<0.05). There was no difference between the two groups in regards to hemoglobin, platelet, MPV, creatinine, ALT, D-dimer, albumin, FAR, NLR, DDAR levels (p<0.05). AST levels were slightly higher in pRP group (p=0.027). Markedly increased WBC, fibrinogen, MPV and MCP-1 values were detected in pRP group (p=0.000). Additionally, higher abnormal FMD responses were detected in pRP group (p=0.000). There was a direct correlation between abnormal FMD response and serum MCP-1 values in patients with pRP (R: 0.308, R2: 0.095, p: 0.044). Conclusion: It seems to be that MCP-1 levels are higher in patients with pRP and increased values of MCP-1 levels seem to be related to impaired endothelial functions