Wernicke encephalopathy (WE) is a rare and serious complication of obesity surgery. This is a report of one case of WE after a sleeve gastrectomy. The diagnosis is primarily clinical; the persistent and prolonged vomiting, and noncompliance to vitamin intake are two major risk factors to develop WE. It is especially important to rule out for stenosis or obstructions of the upper digestive tract after surgery. MRI is useful with high specificity to support the diagnosis as in our case, and discard other causes. Treatment should not be delayed. The outcome of WE is not always predictable. The full recovery is not always achieved, but there is improvement over the time as in this case.