Treatment and prevention of intramammary infections (IMI) represent a large portion of antibiotic use in the dairy industry. Dairy producers have multiple intervention choices to prevent IMI in the dry period, including use of internal teat sealants with or without antibiotics. Generally, producers and advisors are interested in relative efficacy, as opposed to pair-wise comparisons to non-treated controls or a single comparator. Network meta-analysis assesses relative efficacy of multiple interventions through direct and indirect evidence. The objective of this review was to assess the efficacy of teat sealants to prevent new IMI and clinical mastitis in the subsequent lactation. Five databases, relevant conference proceedings, and FDA NADA summaries were searched. Eligible studies assessed teat sealants with or without antibiotics, compared with no treatment or other treatment (e.g., antibiotics alone) in pre-partum heifers or dairy cows at dry-off, and assessed one or more of the following critical outcomes: incidence of IMI at calving, incidence of IMI in the first 30 DIM, or incidence of clinical mastitis in the first 30 DIM. Study screening and data extraction were done independently in duplicate. From 2280 initially identified records, 199 were assessed at full text, with 75 studies containing 82 trials passing this stage. 40 trials had full data extracted, with network meta-analysis performed using 23 trials reporting incidence of IMI at calving. Use of an internal teat sealant significantly reduced the risk of IMI at calving compared with non-treated controls (RR = 0.36, 95% CI = 0.25, 0.72), but the use of any category of antibiotic in addition to teat sealants did not reduce the risk beyond that of teat sealant alone. Exploration of sources of heterogeneity is ongoing. This work revealed important challenges with comparable outcomes, replication and connection of interventions, and quality of reporting of study conduct. Consideration of use of reporting guidelines, standardized outcomes, and inclusion of at least one intervention arm used in other research would increase the value of primary research in this area.