Objective Whipple’s disease (WD) is a systemic, chronic, relapsing disease caused by Tropheryma whipplei , which can mimic signs and symptoms of various clinical entities. Typical manifestations are represented by gastrointestinal and systemic symptoms, among which neurological ones are frequent. We present the case of a patient with WD and rapidly progressive cognitive impairment and a review of literature aimed to report epidemiological, clinical, neuroimaging, and laboratory findings of cognitive impairment associated with WD. Methods A systematic review of medical literature published until November 22, 2020, was performed. Full-text, peer-reviewed case reports and series in English language presenting patients with WD and cognitive impairment were included. Data concerning demographic, clinical, neuroimaging, and laboratory characteristics were collected and synthesized qualitatively. Results The patient was a 54-year-old male who developed rapidly progressive dementia, fluctuating arousal disturbances, and supranuclear ophthalmoparesis associated with chronic diarrhea and fever spikes. T. whipplei was detected in the cerebrospinal fluid, and appropriate antimicrobial therapy was given with progressive clinical benefit. The systematic review of 114 case reports/series identified 147 patients with WD and cognitive impairment; this latter was rarely isolated. Neurological symptoms associated with cognitive decline were psychiatric disturbances, supranuclear ophthalmoplegia, hypothalamic involvement, and consciousness disorders. Brain imaging and cerebrospinal fluid findings were heterogeneous and nonspecific. Conclusions Cognitive impairment represents one of the most common neurological features associated with WD. The clinical suspicion of this disease in patients with rapidly progressive dementia is crucial to guide diagnostic strategies and proper antimicrobial therapy, which may revert the clinical deterioration.