Thalamic dysfunction has been associated with schizophrenia and other psychotic disorders. We describe an adult patient with a lacunar infarct in the posterior region of the right thalamus exhibiting a paranoid schizophrenia-like psychosis as the only clinical manifestation. Neuropsychological assessment showed alterations in visuospatial memory and executive functions at follow up. This case highlights the role of information processing by the thalamus in the development of delusions. We suggest that dysfunction of the right mediodorsal and pulvinar thalamic nuclei disrupts both thalamic sensory processing and thalamo-prefrontal circuits mediating belief evaluation, leading to delusional beliefs.