Abstract Background Multiple sclerosis is a complex disease in which genetic susceptibility plays a role and familial occurrence has long been recognized. To date, no studies of familial occurrence have been conducted in Argentina, a country with low to intermediate prevalence. Methods As part of a cross-sectional study on multiple sclerosis in Buenos Aires, immediate and extended pedigree details were collected on 219 patients. Crude and age-adjusted recurrence risks for patient relatives were also assessed. Results Details on age or age of death and disease status were obtained for 4227 relatives. Ten percent of patients reported at least one relative with MS diagnosis, the highest risk (1.54%) was observed in daughters of patients who presented 92-times greater risk than the general population. Sibling recurrence risk ratio was similar to that reported in other locations. Conclusions Relatives of patients with MS living in Argentina are at greater risk of developing the disease, although not as high as the risk reported for other geographic regions.