More than 30 patients with multiple sclerosis (MS) and Parkinson's disease (PD) have been reported so far. Theories on the co-occurrence of MS and PD range from coincidental to causal. There has been only one report of MS in young onset PD in a patient heterozygous for Parkin mutation. We report a patient with MS who developed signs typical for PD and was found to be heterozygous mutation carrier in the gene for glucocerebrosidase (GBA1), a well-known risk factor for PD. •We report a case of MS patient who developed PD and was found to be heterozygous carrier of GBA1 gene mutation.•MS might increase the chances of PD development in GBA1 gene mutation carriers.•The mechanisms by which GBA1 mutations increase the risk of development PD in the setting of MS are not known.