The pandemic of the coronavirus disease 2019 resulted in an increased prevalence of social isolation and loneliness. Cox proportional hazards regression was used to test the association between social isolation/loneliness, multiple cardiometabolic diseases (CMDs) and cardiometabolic multimorbidity (CMM). In the multivariable adjusted models, compared with the least isolated, the most isolated had independently associated with CMD (HR 1.07, 95% CI 1.03 to 1.11) and CMM (HR 1.24, 95% CI 1.12 to 1.36) in stage I, and CMM in stage II (HR 1.14, 95% CI 1.05 to 1.23). Compared with those with the least loneliness, those who with most loneliness had about 20% increased risk of CMD and 29% increased risk of CMM in stage I. Those with the most loneliness were also significantly associated with increased CMM risk (HR 1.30, 95% CI 1.19 to 1.42) in stage II. This study revealed the associations of social isolation/loneliness with CMD and CMM.