Adiponectin is a peptide hormone secreted from the adipose tissue, affecting the proliferation and insulin sensitivity in different cell types. The levels of adiponectin have been found to be decreased in hyperinsulinemia and insulin resistant states, such as obesity. The previous studies have suggested that plasma adiponectin levels are decreased in patients with endometrial and breast cancer. In our study, the relationship among serum adiponectin levels, demographic features and histopathological variables was evaluated in gastric cancer patients. Forty consecutive patients with gastric cancer who underwent gastrectomy with standard lymph node dissection were included and 43 healthy controls were included in this study. The serum levels of glucose, insulin, C-peptide, HbA1c and adiponectin were measured in both groups. We analyzed the correlation among these parameters and patients' demographic features, such as age, gender, body mass index (BMI) and histopathological variables such as tumor localization, stage, nodal status, histological grade, vascular and lymphatic invasion. The mean age was 60.05 + 9.72 in patients, while it was 38.6 + 12.73 in controls. The mean serum adiponectin levels were 12.62 + 7.9 and 10.07 + 6.72 ng/ml, respectively, in groups. There was no different in terms of adiponectin, C-peptide, HOMA-R level in both groups. On the other hand, BMI, glucose and insulin levels were significantly different in gastric cancer patients in comparison with the controls. There was no correlation among the levels of adiponectin, BMI, insulin and c-peptide levels in patient group (P > 0.05). The adiponectin levels of woman were significantly lower than male patients (P = 0.002). No relations were detected among tumor stage, tumor localization, nodal status, lymphatic and vascular invasion, and the levels of serum adiponectin (P > 0.05). Interestingly, a positive correlation was found between tumor grade and plasma adiponectin levels (r = 0.372; P = 0.018). Our results suggest that plasma adiponectin levels were similar in both patients with gastric cancer and the controls. In addition, no correlation was found between adiponectin levels and demographic features and histopathological variables of patients. But, in undifferentiated tumors, plasma adiponectin level was significantly higher than well-differentiated grade tumors.