Background The association of a healthy lifestyle with the prognosis of type 2 diabetes remains uncertain. We aimed to evaluate the associations of a healthy lifestyle and a higher American Heart Association's Life's Essential 8 score with incident macrovascular and microvascular diseases in type 2 diabetes. Methods and Results A total of 13 543 participants with baseline type 2 diabetes and free of macrovascular and microvascular diseases from the UK Biobank were included. A healthy lifestyle was determined based on body mass index, smoking, alcohol consumption, physical activity, sleep duration, and diet. Life's Essential 8 scores were generated from 8 metrics according to the American Heart Association's cardiovascular health advisory, ranging from 0 to 100. During a median follow-up of 12.1 years, 3279 (24.2%) incident macrovascular diseases and 2557 (18.9%) microvascular diseases were documented. Compared with those with a poor lifestyle, participants with an ideal lifestyle had significantly lower risks of incident macrovascular disease (hazard ratio [HR], 0.46 [95% CI, 0.36-0.59]) and microvascular disease (HR, 0.60 [95% CI, 0.47-0.77]). Significantly lower risks of macrovascular disease (HR, 0.20 [95% CI, 0.05-0.79]) and microvascular disease (HR, 0.24 [95% CI, 0.06-0.98]) were also found in the high cardiovascular health group (Life's Essential 8 scores: 80-100), compared to the low cardiovascular health group (scores: 0-49). Adhering to an ideal lifestyle may prevent 37.0% of macrovascular disease and 24.7% of microvascular disease, and attaining a high cardiovascular health may prevent 71.9% of macrovascular disease and 67.5% of microvascular disease. Conclusions A healthy lifestyle and a higher Life's Essential 8 score were associated with lower risks of macrovascular and microvascular diseases among participants with type 2 diabetes.