The loggerhead turtle (Caretta caretta) is one of the most iconic, yet vulnerable, species of marine megafauna. A well-established concept in marine turtle ecology is that C. caretta migrates between oceanic and neritic habitats, changing its foraging strategies throughout its life history. This study aims to shed light on the diet of C. caretta in the Mediterranean Sea by combining a systematic review with a stable isotope analytical approach. Data extracted from sixteen original articles were analysed using multivariate techniques revealing high variability in the feeding habitat (benthic vs. pelagic), while life-stage-based dietary segregation did not occur. This unexpected result may reflect publication biases in the definition of life-stage thresholds and associated dietary shifts, or perhaps the need to revise the classic pelagic–benthic ontogenetic shift paradigm. To explore this further, we analysed stable isotope data from multiple tissues with different turnover rates, collected from juvenile to adult loggerhead sea turtles stranded along the Sicilian coasts from 2021 to 2025. These data suggest, in contrast, a gradual dietary and trophic-level shift with growth, with juveniles relying more on low-trophic level pelagic prey and adults on high-trophic level benthic prey. Sub-adults also appear to change their dietary patterns over time, consistent with ontogenetic dietary transitions. Moreover, differences in isotopic results among tissues with different turnover rates emerged, with interesting implications for the understanding of recent versus past dietary patterns. Overall, these findings highlight critical knowledge gaps and biases in the existing literature and emphasize the need for additional empirical data to strengthen current knowledge on sea turtle trophic ecology and inform effective conservation strategies for C. caretta in the Mediterranean Sea.