It concerned diabetic patients followed in Brazzaville and Pointe-Noire agreeing to the study, after obtaining the opinion of the ethics committee of the research in health science. All samples collected were screened for the presence of anti HCV Ab using a rapid ALERE HCV test and the Monolisa HCV Ag-Ab ultra test for confirmation in Congo. Detection of the viral RNA was done by PCR retrotranscription and genotyping was performed according to the reverse hybridization technique in France. Data analysis was done with EpiInfo 6.0 software (2016); the proportions were compared using the Chi-square test or the Fisher test at the significance level of 5%. Results: Of 447 patients with diabetes mellitus, 49 had HCV positive serology and the sex ratio was 0.63. Seroprevalence of AC anti HCV was 11% (49/447); HCV RNA was detectable in 71.4% (n = 35) patients. The average age of the population was 62 ± 10 years with extremes ranging from 26 to 82 years. The circulating genotypes were 4 (97.1%) and 1 (2.8%). Subtyping was defined in 17.64% (n = 6) of genotype 4 patients; undefined in 82.36% (n = 28) of Genotype 4 patients, and in one of genotype 1 patients. The subtypes identified were subtype 4e (60%), subtype 4e (8.8%), subtype 4a/4c/4d (5.8%), and subtype 4h (2.9%).