To examine the association between blood urea nitrogen (BUN) and risk of type 2 diabetes (T2DM) among Chinese adults, we performed an ongoing cohort study of 38578 Chinese adults (56.3% males; average age, 41.6 y) who underwent repeated health check-up examinations between 2009 and 2016 and without T2DM at baseline. During follow-up, incident T2DM cases were identified based on self-report, medication use, measurements of fasting plasma glucose, 2 h post oral glucose, or haemoglobinA1c. 2009 (5.2%) cases confirmed with incident T2DM were identified during median follow-up of 3.1 years. With increasing quartiles of BUN levels, the incidences of T2DM gradually increased with 0.69%, 1.11%, 1.53%, and 1.87% for quartile 1 to quartile 4 (p trend <0.001). Compared with quartile 1, the multivariate-adjusted hazard ratios (HRs) and its 95% confidence intervals (95% CIs) for T2DM risk were 1.16 (0.97–1.38) for quartile 2, 1.28 (1.07–1.51) for quartile 3, and 1.28 (1.08–1.52) for quartile 4 (p trend = 0.005). HR for per each standard deviation increase in BUN level was 1.10 (1.04–1.16) (p trend <0.001). This association tended to be more pronounced in those with a lower body mass index at baseline (p-interaction <0.001). Our results suggested that BUN levels were positively associated with incident T2DM risk among Chinese adults. Future prospective investigations in other populations are necessary to confirm our findings.