When harvested or raised within sustainable systems, products of domestic fisheries and aquaculture offer healthy, affordable seafood choices with minimal environmental impact that can help Americans meet dietary guidelines for seafood intake. However, some consumers hesitate to purchase seafood products, associating them with negative environmental impact, and adherence to intake recommendations remains low. Consistent sustainability labeling on seafood products could better signal environmental responsibility and encourage consumers toward increased intake. To characterize label attributes indicative of sustainability on seafood packages. A content analysis of seafood package labels was conducted using the Label Insight product database. Characterized attributes included 320 terms and certifications documented on packages. From over 400,000 food products, 2,200 seafood packages were selected for inclusion based on type: salmon (n = 730), shrimp (n = 1,387), and oysters (n = 83). Mixed dishes were excluded. Four trained coders characterized label attributes according to a priori themes, including sustainability. Total usage frequencies of sustainability-related labels, and frequencies of specific terms and certifications, were determined for each seafood type. Pearson chi-square analyses were conducted to evaluate statistical associations between seafood type and sustainability labeling practices. Thirty-eight attributes (11.9%) were coded as sustainability labels. Overall, more salmon (47.9%) and shrimp (47.6%) packages displayed sustainability labels than did oysters (26.5%), (χ2 (2, N = 2,200) = 14.443, P = 0.001). Specific terms used varied by seafood type. Salmon (41.6%) and oyster (26.5%) packages displaying sustainability labels most frequently utilized unstandardized “environmental” terms, whereas shrimp packages (36%) most often displayed a third-party sustainability certification label. Lesser-used terms included planet friendly, responsibly produced, and responsibly caught. While encouraging that nearly half the evaluated salmon and shrimp packages reference sustainability, use of terminology and certifications across and within seafood types is inconsistent. Future studies might investigate whether more frequent use of standardized sustainability labels measurably increases seafood purchase and consumption.