Substance use disorder (SUD) is a complex condition involving psychological, sociocultural, and genetic factors. In this study, we examined the alternations in mitochondrial DNA copy number (mtDNAcn) and telomere length (TL) and their relationship to demographic, medical, heredity, and substance use characteristics in patients with SUD and healthy controls. We investigated a total cohort of 54 participants: 21 healthy individuals, 17 patients with alcohol dependence (AD), and 16 patients with drug dependence (DD). TL and mtDNAcn were measured using quantitative real-time PCR, with statistical methods used to assess the association between variables. We observed a significant decrease in mtDNAcn in both SUD groups, particularly associated with chronic diseases in the AD group. No significant differences in TL were found among the three groups. Sex-associated analysis revealed a significant mtDNAcn reduction in the DD males and elevated TL in AD males compared to control males. Correlation analyses showed associations between the two biomarkers and age, sex, and chronic diseases. Our findings suggest that leukocyte mtDNAcn is a more sensitive marker than TL in patients with SUD, indicating sex-specific patterns of alterations. These findings require confirmation through larger cohort recruitment.