Type 1 diabetes mellitus (T1D) is associated with an increased risk of cardiovascular disease (CVD) that begins in childhood. Youth with T1D develop concerning functional cardiac and vascular defects and evidence of early atherosclerosis, despite modern advancements in risk reduction and glycemic management. Such early defects predict poor long-term outcomes. Women with T1D also have higher CVD risk than expected for unexplained reasons. Insulin resistance (IR) is recently recognized as a prominent factor in T1D youth and adults, but with an atypical clinical phenotype. This IR may contribute to early cardiac and vascular dysfunction and long-term CVD in T1D. A better understanding of potential contributors to cardiovascular dysfunction in T1D youth such as IR and its unique phenotype in T1D, subtle lipid abnormalities, and gender differences is now required to address the current knowledge gaps and to prevent cardiovascular morbidity and mortality in T1D.