Background/Aims The relationship between C-peptide levels and gastrointestinal (GI) symptoms in type 2 diabetic patients is not clear. The purpose of this study is to examine the association between fasting C-peptide and GI symptoms of gastroparesis in type 2 diabetic patients. Methods We recruited 333 type 2 diabetic patients into the present study. All patients filled out questionnaires of gastroparesis cardinal symptom index (GCSI) to evaluate GI symptoms. Hospital anxiety and depression scale were adopted to define anxiety and depression. Patients with GCSI scores >= 1.9 were regarded as having symptoms of gastroparesis. Results In our study, 71 (21.3%) type 2 diabetic patients had GCSI scores >= 1.9. In comparison to patients with scores < 1.9, those with scores >= 1.9 had significantly lower fasting c-peptide levels (1.49 ng/mL vs 1.94 ng/mL, P < 0.001), higher prevalence of depression (40.9% vs 18.3%, P < 0.001) and anxiety (28.2% vs 13.0%, P = 0.002). Multivariate logistic regression revealed that fasting C-peptide was still significantly associated with symptoms of gastroparesis (odds ratio, 0.67; 95% confidence intervals, 0.48-0.94; P = 0.021), even after adjustments for age, sex, body mass index, HbA1c, current smoking and drinking status, anxiety, and depression. Furthermore, linear regressions showed that fasting C-peptide was independently and negatively related to GCSI scores (standardized regression coefficient, -0.29; P < 0.001) in patients with at least one GI symptom. Conclusion GI symptoms of diabetic gastroparesis affect approximately 20% of type 2 diabetes patients and are associated with lower fasting C-peptide levels independent of depression and anxiety status.