We examined the psychometric properties (internal consistency, concurrent criterion validity, and known-group validity) of the Loewenstein Occupational Therapy Cognitive Assessment (LOTCA) in people with intellectual disabilities. A total of 111 people with intellectual disabilities and 19 people with no disabilities were included. We used Cronbach's alpha, Spearman's rho, the Kruskal–Wallis test, and one-way analysis of variance for analysis, where appropriate. Results showed good internal consistency on Orientation, Visual Perception, Spatial Perception, Visuomotor Organization, and Thinking Operations subscales (Cronbach's αs = .82, .74, .76, .86, and .80, respectively), but not on the Motor Praxis subscale (α = .48). We found significant correlations between participants’ performance on the Pictorial IQ test and disability level and scores on the LOTCA. The known-group validity of the LOTCA in people with intellectual disabilities was satisfactory. We concluded that the LOTCA is a suitable instrument for measuring cognitive abilities and visual perception in people with intellectual disabilities.