Objective The aim of this study was to evaluate the resistin concentrations in saliva; which is a noninvasive and stress-free diagnostic sample, and to investigate the significance of salivary resistin concentrations in screening GDM. Methods This cross-sectional case-control study included 41 newly diagnosed GDM patients and 40 healthy pregnant. The participants were consecutively included in the study among eligible pregnant women; who were in the age range from 18 to 40 years of age and at the gestational age between 24 and 28 weeks. The levels of serum and salivary resistin were determined using an enzyme-linked immunosorbent assay method. Results Maternal serum resistin and salivary resistin concentrations were significantly higher in the patients with GDM compared to the individuals in the control group. The data were evaluated by the receiver-operator curve analysis; which revealed that serum and saliva resistin concentrations were moderately successful markers to differentiate subjects with GDM from healthy pregnant women. Conclusions The results indicate that the determination of saliva resistin levels at the gestational age between 24 to 28 weeks may be used as an alternative, stress-free, and noninvasive technique that may be used in GDM screening.