Sea turtles are long-lived migratory species that are sensitive to anthropogenic impacts. Their condition reflects that of marine ecosystems and can serve as an indicator for environmental monitoring. However, evaluating body condition parameters, as a proxy for health, is challenging and often overlooked. The purpose of this study was to validate a straightforward method for assessing the body condition of nesting loggerhead sea turtles (Caretta caretta), and to investigate whether body condition was correlated with epibiont loading. To achieve this, 60 nesting loggerhead sea turtles were sampled and categorized into five body conditions ranging from very poor to very good. Injuries, skin deformities and plastron shape were used for this classification. Epibionts were collected from the same turtles and identified, with species richness, diversity, community structure and barnacle loading compared among body conditions. Epibiont communities were correlated with body condition as both species richness and abundance increased with a decline in turtle body condition. Barnacle epibionts showed great variation among different body conditions, having significantly higher numbers on turtles in poor condition. All parameters in this study showed similar distinctive relationships with body condition of loggerhead turtles from poor to very good body condition. The body condition index used in this study can be applied readily and, along with barnacle counts, can provide basic baseline information on turtle health.