OBJECTIVE: The purpose of this research is to investigate the effect of High Intensity Interval Training and Resistance training (HIITR) on heart rate variability (HRV), blood glucose, and plasma biomarkers levels in adolescents with type 1 diabetes (T1D). RESEARCH DESIGN AND METHODS: 24 boys with T1D (FBS: 274.66 +/- 52.99, age: 15.2 +/- 1.78 years, and BMI = 19.61 +/- 1.11) and 12 healthy boys (FBS: 92.75 +/- 5.22, age: 15.08 +/- 1.67 years, and BMI = 20.26 +/- 2.66) were divided into three groups: Diabetes Training (DT, n = 12), Diabetes Control (DC, n = 12), and Healthy Control (HC, n = 12). HRV (24 h) was computed in time and frequency domains, anthropometric, biochemical parameters at rest, and aerobic capacity (VO(2peak)) obtained during a graded exercise testing (GXT). All variables were evaluated at the baseline and following 12 weeks of exercise training, done 3 days weekly. The statistical method used for data analysis was analysis of covariance (ANCOVA) test. RESULTS: HRV, Hemoglobin A1c (HbA1c) and Fasting blood sugar (FBS), VO(2peak), norepinephrine (NEP), and HDL-C indicated significant differences between both T1D groups compared to HC at baseline (p < 0.001). BMI, LDL-C, TC, and TG parameters were similar in all groups. HRV parameters, VO(2peak) and HDL-C, and NEP were significantly improved by exercise training, and HbA1c and FBS levels were significantly reduced (p < 0.001). There is a negative and significant correlation between LF/HF Ratio Difference (post-test minus pre-test) and VO2Peak Difference variables (post-test minus pre-test) (p < 0.001). CONCLUSIONS: The present study suggests the importance of early screening for CVD risk factors in adolescent males with T1D. Also, it was revealed HIITR training compared to other training patterns, and cardiovascular health improves via enhancement of autonomic modulation, VO(2peak), plasma lipids, and catecholamine levels.