The article describes the case of a patient with Wernicke encephalopathy, which developed 3 months after the sleeve gastrectomy. An MRI of the brain was performed to verify the diagnosis, which revealed a symmetrical non-uniform increase in the MR signal on T2-WI and Tirm from the medial part of the thalamus, mastoid bodies and gray matter around the aqueduct of Sylvius. Thiamine infusion was promptly initiated as therapy. During treatment, acute neurological symptoms almost regressed, the patient was discharged in a satisfactory condition with preservation of vertical nystagmus under the supervision of specialists at the place of residence. Wernicke–Korsakoff syndrome more often occurs as a complication of alcoholism and arising from thiamine deficiency. However, the fact that this condition also occurs under the influence of other etiopathogenetic factors is often ignored by clinicians. In the management of patients after bariatric interventions, this condition is much more common in malabsorptive operations. However, a combination of certain factors can be described in patients after restrictive types of bariatric surgeries.