Twenty percent of all schizophrenic patients experience sexual delusions at some point during the evolution of their illness. Among them, some patients develop the conviction of belonging to the other sex. Although true coexistence of schizophrenia and gender identity disorder is rare, it can be difficult to disentangle the two conditions. We report the case of a 40-year-old male patient with chronic schizophrenia who developed intrusive gender identity preoccupations over the years. Using this clinical case as a starting point, relevant literature is then reviewed and discussed. Long-lasting florid delusions of sex change are unusual but have been noted among patients with schizophrenia. Considering the irreversible consequences of surgery and its medico-legal implications, these patients should be properly detected.