Few studies have investigated the relationship between low dietary variety and clearly defined social isolation by gender. This study explored the association between dietary variety and social isolation, classified by operational definition, separately by gender in community-dwelling older adults. This cross-sectional study recruited respondents via mail. A total of 4798 participants aged ≥65 years participated in the on-site assessment. Social isolation was assessed by "lack of conversation," "lack of passive support," "lack of offering support," and "lack of social participation." Dietary variety was evaluated using the Dietary Variety Score (DVS). The participants' median age was 73 (interquartile range 25-75: 69-77) years, and 2147 (44.7%) were male. After adjusting for covariates, with regard to male participants, a lack of offering support (β = -0.051, P = 0.019) and a lack of social participation (β = -0.089, P < 0.001) were associated with a low DVS. For female participants, only a lack of social participation was related to a low DVS (β = -0.067, P < 0.001). A lack of conversation and passive support were not associated with a low DVS for both genders (P >0.05). The results indicate that encouraging social participation, regardless of gender, as well as preventing a lack of offering support for others among men, may contribute to improving individuals' DVS. Geriatr Gerontol Int 2024; ••: ••-••.