Capgras syndrome (CS) is a delusional misidentification syndrome that is encountered in various pathologies. Here, we report the case of an 83-year-old woman affected by dementia with Lewy bodies who presented a CS during the disease. The neuropsychological assessment showed executive and face processing deficits. In this case, CS was characterized, in the beginning, by the duplication of a relative and then by its multiplication. To our knowledge, the description of the evolution of a CS in the course of a neurodegenerative disease is rare and we discuss this multiplication phenomenon in light of existing models of delusions.