Aims Patients with type 1 diabetes have a high risk of cardiovascular disease. Yet, the importance of routine assessment of myocardial function in patients with type 1 diabetes is not known. Thus, we examined the prognostic importance of NT-proBNP and E/e', an echocardiographic measure of diastolic function, in type 1 diabetes patients with preserved left ventricular ejection fraction (LVEF) and without known heart disease. Methods and Results Type 1 diabetes patients without known heart disease and LVEF ≥ 45% enrolled in the Thousand and1 study were included and followed through nationwide registries. The risk of major cardiovascular events (MACE) and death associated with levels of NT-proBNP and E/e' was examined. Of 960 patients, median follow-up of 6.3 years (Q1-Q3: 5.7-7.0), 121 (12%) experienced MACE and 51 (5%) died. Increased levels of both NT-proBNP and E/e' were associated with worse outcomes (adjusted hazard ratios for MACE = 1.56 (1.23-1.98) and 4.29 (2.25-8.16) per Loge increase for NT-proBNP and E/e', respectively). NTproBNP and E/e' combined significantly improved the discrimination power of the Steno T1D risk engine (MACE, C-index: 0.813 (0.779-0.847) vs 0.779 (0.742-0.816); P=0.0001; All-cause mortality, C-index 0.855 (0.806-0.903) vs 0.828 (0.776-0.880); P=0.03). Conclusion In patients with type 1 diabetes, preserved ejection fraction, and no known heart disease, NT-proBNP and E/e' were associated with increased risk of MACE and all-cause mortality. The risks associated with NT-proBNP and E/e' combined identified patients at remarkably high risk.