Aims We investigated the incidence and clinical features of venous thromboembolism (VTE) in inpatients with mental illnesses. Methods We retrospectively analyzed records of inpatients with mental illnesses and confirmed VTE at The First Hospital of Hebei Medical University between August 2018 and July 2022. We recorded demographic characteristics, psychosis-related conditions, and thrombus distribution. Results Among 12939 patients diagnosed with mental illness, 156 (1.21%) presented with VTE at the first visit or during the disease course. Crude VTE incidence varied significantly across mental illnesses, being highest in patients with organic mental disorders (5.20%), followed by emotional disorders (1.10%), and others ( P < 0.001). Distal and proximal deep venous thromboses (DVT) occurred in 79.17% and 20.84% of patients, respectively. The Hamilton Depression Scale (HAMD) score was higher in patients with proximal DVT than in those with distal DVT ( P < 0.001). On multivariate analysis, the HAMD score (odds ratio [OR] 1.173, confidence interval [CI] 1.100−1.251, P<0.001) was a risk factor and the Hamilton Anxiety Scale (HAMA) (OR 0.862, CI 0.796−0.934, P<0.001), a protective factor against DVT progression. Conclusion VTE is not rare in patients with mental illnesses and is most commonly associated with organic mental disorders. Psychosis-related DVT typically shows a significantly high incidence of distal DVT. Prevention and early treatment in patients with severe depression and distal DVT can prevent DVT aggravation.