Background: Psoriasis is acknowledged for its association with diabetes and obesity. However, the comprehension of the correlation between obesity and psoriasis risk in individuals with diabetes remains limited. Objective: We aimed to examine the association of body mass index and waist circumference (WC) with the risk of developing psoriasis in individuals with type 2 diabetes mellitus (T2DM). Methods: This retrospective cohort study utilized nationwide data for exploratory analysis.A total of 2,480,489 participants, all diagnosed with T2DM, were included. Results: Over a 6.77±1.69-year follow-up, 71,514 patients (2.88%) were diagnosed with psoriasis. Adjusting for multiple variables, the study revealed a J-shaped pattern association between BMI levels and the hazard ratio (HR) for psoriasis in patients with T2DM. A linear pattern relationship was observed regarding WC, with the highest WC group showing the most elevated HR (HR, 1.123; 95% confidence interval, 1.091–1.156). Conclusion Understanding the relationship between psoriasis risk and obesity in diabetic individuals holds the potential to enhance the management of patients with T2DM.