The association of thyroid disorders and thyroid-related treatments with psychiatric disorders is well known. What is not recognized yet is if antithyroid antibodies may cause psychosis in the absence of encephalopathy and thyroid dysfunction. I report here the cases of 4 patients who developed de-novo psychosis where I found they had high titers of antithyroid antibodies, both antithyroglobulin and antiTPO antibodies. All the four patients were women aging 39-64 years old, without history of psychiatric disorders until they started with an isolated and flourished picture of psychosis. Remarkably, thyroid function was normal. All four cases showed positive CSF thyroid antibodies and recovered after steroid therapy.I propose to coin the term “antithyroid psychosis” to denote cases of de-novo psychosis with antithyroid antibodies in the absence of encephalopathy. The main importance of diagnosing these cases is that it is a tractable disorder. Screening for antithyroid antibodies should be considered in all patients with de-novo psychosis or postpartum psychosis.