Abstract Accumulating evidence has shown that poor oral hygiene is associated with increased risk of cardiometabolic diseases in Western populations. However, its relevance about the relationships in Chinese adults remains unclear. The China Kadoorie Biobank enrolled 512 715 adults aged 30‐79 years in China during 2004‐2008. Cox regression was used to estimate adjusted hazard ratios (HRs) for each disease associated with measures of oral hygiene. Overall 9.3% of the participants reported rarely or never brushing teeth at baseline. Participants who rarely or never brushed teeth had adjusted HR of 1.12 (95% CI: 1.09, 1.15) for MVE, with similar HRs for stroke (1.08, 1.05‐1.12), intracerebral haemorrhage (1.18, 1.11‐1.26) and pulmonary heart disease (1.22, 1.13‐1.32) compared with those who brushed teeth regularly. Those who did not brush teeth also had increased risk of cancer (1.09, 1.04‐1.14), chronic obstructive pulmonary disease (COPD) (1.12, 1.05‐1.20), liver cirrhosis (1.25, 1.09‐1.44) and all‐cause death (1.25, 1.21‐1.28) but not type 2 diabetes (0.94, 0.86‐1.03) and chronic kidney disease (0.98, 0.81‐1.18). Among Chinese adults, we found that poor oral hygiene is associated with higher risks of major vascular disease, cancer, COPD, liver cirrhosis and all‐cause deaths, but not type 2 diabetes and chronic kidney disease.