<p><b>AIMS: </b>To examine the association of social capital with periodontal disease severity.</p><p><b>MATERIALS AND METHODS: </b>We analysed data obtained from 3,994 men and women aged 18-74 years in the Hispanic Community Health Study/Study of Latinos Sociocultural Ancillary Study (HCHS/SOL SCAS). From 2008 to 2011, dentists assessed periodontitis status with a full-mouth periodontal examination. Periodontitis was classified using standardized case definitions. Multivariable logistic regression estimated odds of moderate-severe periodontitis associated with two measures of social capital: structural support (Social Network Index) and functional support (Interpersonal Support Evaluation List).</p><p><b>RESULTS: </b>For US-born participants, for each additional person in their social network, the adjusted odds of moderate-severe periodontitis was reduced 17% (OR = 0.83, 95% CI = 0.71, 0.96). However, no association was found between functional support and periodontal disease severity.</p><p><b>CONCLUSIONS: </b>Greater structural social support was associated with a lower prevalence of moderate-severe periodontitis in US-born Hispanics/Latinos. These findings suggest that US-born Hispanics/Latinos with less social support represent a vulnerable segment of the population at high-risk group for periodontal disease.</p>