Leukocyte telomere length (LTL) is considered a reliable biological indicator of aging. LTL shortening has been associated with an increased risk of cardiometabolic markers among adults. However, evidence for an association in adolescents is limited. This cross-sectional study examined the association between blood biomarkers of cardiovascular diseases and leukocyte telomere length in 59 Thai adolescents with mean age 15 years. Blood samples and anthropometric, clinical, and biochemical data were collected, with relative telomere length (RTL) measured using the quantitative polymerase chain reaction (qPCR) method. Results showed that RTL was negatively associated with Hemoglobin A1C (HbA1C) but positively associated with high density lipoprotein cholesterol (HDL-C). Inflammatory Tumor necrosis factor alpha (TNF-α) was positively correlated with RTL, with a strong association in female adolescents. After adjusting the confounding factors including age, gender, and body mass index (BMI) for age the multivariable models indicated that predictors of shortening RTL were higher levels of HbA1C ( = -0.444,  = 0.002) and lower in HDL-C ( = 0.025,  = 0.002). The results suggested a positive association between telomere length and cardiometabolic risk factors such as HbA1C and HDL-C in Thai adolescent subjects. To confirm these findings, a longitudinal study should be conducted in the future with a larger sample size with considering of environment factors.