We evaluated the responses of 16 patients to preliminarily explore the spectrum of effectiveness and tolerability of the memantine, and NMDA antagonist, in the treatment of dementia in Wernicke-Korsakoff syndrome. In this study, for the first time in dementia of Wernicke-Korsakoff syndrome, the response to memantine was assessed. 16 patients with median age of 64 years and median body weight of 77 kg were treated with memantine 10 mg twice daily for up to 28 weeks. Clinical global impressions (CGI), and Mini Mental Status Examination (MMSE) were performed during the treatment period (after 2, 4, and 28 weeks). Efficacy measures also included the ADCS-Activities of Daily Living scale (ADCS-ADL). At 28 weeks, the ADCS-ADL showed significantly less deterioration in memantine treated patients compared with placebo (-2.3 compared with -4.3: p = 0.005). The results of MMSE demonstrate a significant and clinically relevant benefit for memantine relative to placebo as shown by positive outcomes in cognitive and functional assessments. Memantine (10 mg) was safe and well tolerated. The preliminarily findings of this study with 16 patients suggested that memantine is effective in the treatment of dementia in Wernicke-Korsakoff syndrome.