Catatonia occurring as part of a clinical picture of dementia has been reported with almost all types of dementia. It remains under-diagnosed in older adults and those with dementia. We review a case of a young patient admitted in our psychiatric department for catatonia and after efficient treatment with Lorazepam, assessment revealed a dementia. Catatonia is a severe neuropsychiatric syndrome with an excellent prognosis if recognized and treated without delay.