Purpose: Severe Hypomagnesaemia is a rare biochemical findings utilized for identifying the etiology of cerebellar ataxia. It requires a high degree of suspicion to diagnose. MRI findings are often nonspecific. Methods: The author presents a case of 38 yrs. old male patient presented with vomiting, gait imabalance and nystagmus. Biochemical investigations lead to severe hypomagnesaemia. Also MRI findings were matched suggesting of hyperintesity in left cerebellar hemisphere. Results: Patient was treated with magnesium infusion which leads to recovery of patient. Again the same symptomology was repeated after 3 months and disappearance after same treatment. Offending cause was diagnosed and proton pump inhibitors stopped. Conclusion: Severe Hypomagnesaemia is a rare but treatable cause if diagnosed at right time. It requires a high degree of suspicion to diagnose it. Measurement of serum magnesium levels should always be kept in back of mind if definite management of cerebellar symptoms has to be done.