BACKGROUND: Evidence indicates that fewer non-Hispanic black versus non-Hispanic white youths with type 1 diabetes are meeting treatment goals for optimal glycemic outcomes, predisposing them to risks for cardiovascular (CV) morbidity and mortality in adulthood. PURPOSE: We sought to assess the association of sex and race with heart rate variability (HRV) and cardiorespiratory fitness in adolescents with type 1 diabetes. The association between the HRV and cardiorespiratory outcomes with glucose control was also examined. METHODS: A secondary data analysis of 95 adolescents with type 1 diabetes (n = 66 non-Hispanic white n = 29 non-Hispanic black) was used. Using 24-hour Holter recordings, spectral and time domain measures of HRV were obtained. Cardiorespiratory fitness using a graded exercise test was completed. Descriptive statistics and Pearson correlation coefficients were used to assess associations between glucose control and study outcomes, and general linear models were applied to explore and quantify associations of sex and race with HRV and cardiorespiratory fitness. RESULTS: Body mass index (mean [standard deviation]) was similar between non-Hispanic black (23.5 [3.9]) and non-Hispanic white (22.7 [3.8]) adolescents. Females and non-Hispanic black adolescents had significantly lower HRV and cardiorespiratory fitness levels. Moderate associations were found between lower HRV and poorer glycemic control (HbA1c). Recent HbA1c was significantly higher in non-Hispanic black (9.7 [1.8]) than non-Hispanic white (8.2 [1.2]). CONCLUSION: Findings support the importance of early identification of CV health risks in adolescents with type 1 diabetes, particularly for non-Hispanic black adolescents. Interventions focused on overall improvement in glycemic control for adolescents with type 1 diabetes are a priority for minimizing future CV complications.