Background : Immunological and biochemical parameters are gaining more and more importance in the prognosis of diabetes and its complications. Here we assessed the predictive power of immunological parameters correlated with biochemical ones in gestational diabetes mellitus (GDM). Material and Methods : 217 pregnant women were screened for GDM between the 2 nd and the 3 rd trimester of gestation, based on IAGDP methods in this cross-sectional descriptive study. Immunological and biochemical parameters were determined using appropriate methods. Receiver operating characteristics (ROC) curve analyses were conducted to assess the optimal cutoff and value of immunological to biochemical parameter ratios for predicting GDM. Results : 11.90% of pregnant women were diagnosed GDM positive. Serum glucose levels, total cholesterol, LDL-cholesterol, triglycerides and total proteins were significantly increased while HDL-cholesterol decreased in women with GDM compared to controls. The levels of glycosylated hemoglobin and creatinine, as well as transaminase (AST and ALT) activities did not significantly differ between GDM and pregnant controls. Total leucocytes (white blood cell), lymphocyte and platelet numbers were significantly higher in women with GDM than in pregnant controls. We also found that the lymphocyte:HDL-C, monocyte:HDL-C and granulocyte:HDL-C ratios were significantly higher in women with GDM than in pregnant controls ( p = 0.001; p = 0.009 and p = 0.004 respectively). Women with a lymphocyte:HDL-C ratio greater than 3.66 had a 4-fold increased risk of developing GDM than those with lower ratios (odds ratio 4.00; 95% CI: 1.094 – 14.630; p =0.041). Conclusion : The lymphocyte:HDL-C, monocyte:HDL-C and granulocyte:HDL-C ratios may represent valuable makers, and the lymphocyte:HDL-C ratio in particular may have strong predictive power for GDM. This ratio can be easily assessed in patients.