The prevalence of vitamin B12 nutritional deficiency increases with age and it is particularly common in elderly people. The objective this study was determining its prevalence and the factors associated with this condition in non-institutionalized elderly from Viçosa, Minas Gerais State, Brazil. a cross-sectional, population-based study was conducted in order to identify the prevalence and the factors associated with vitamin B12 deficiency among the elderly population in Viçosa (MG). Data were collected from August 2011 to June 2012, by means of a household survey and hematological and biochemical tests performed in 340 elderly. the prevalence of vitamin B12 deficiency in this group was 17.4% (95% CI, 13.4% - 21.4%). Cognitive impairment appears to be an important factor related to vitamin B12 deficiency. the current paper contributes to studies that emphasize some factors that may affect elderly performance in their natural aging process, especially when these factors are associated with cognitive impairment and lead to significant disability and loss of quality of life. Thus, the herein presented results were able to provide more comprehensive knowledge on the relation between B12 deficiency and its impact on this population. They also proved to be relevant for planning public health programs and initiatives that target on this age group.