Basal eusuchians diversified during the Early Cretaceous and paved the way for the radiation of modern crocodylians. While several neosuchians and eusuchians (e.g. Allodaposuchidae, Bernissartidae, Susisuchidae) already display the classic semi-aquatic bauplan, Hylaeochampsa vectiana OWEN 1874 from the Early Cretaceous of the Isle of Wight (UK) displays an extremely derived morphology, questioning the stem condition for the Eusuchia as well as its paleoecological preferences. Here, we investigate the endocranial morphology of Hylaeochampsa vectiana using microtomographic data and reconstruct its brain endocast, inner ear, associated nerves and blood vessels, and paratympanic and paranasal sinuses. Using these new data, we independently confirm the subadult pedomorphic condition of this taxon. Hylaeochampsa vectiana retains characters with some taxa lying at the neosuchian-eusuchian transition, including a flat endocast and the retention of a prooticparietal connection in the paratympanic sinus system as in Paralligator and Koumpiodontosuchus. Although previously considered closely related, we also recognize important endocranial differences between Hylaeochampsa vectiana and Allodaposuchidae, inviting to reevaluate their phylogenetic affinities. Given the high number of derived characters as well as the shared morphology of the paratympanic sinus with Caimaninae, we recommend not to use Hylaeochampsa vectiana to root characters in phylogenetic analyses of the Eusuchia. Further investigation of basal eusuchian phylogenies should await a wider sampling of other taxa such as Acynodon spp. and Iharkutosuchus makadii in order to better understand endocranial character variability and how to incorporate those into phylogenies. Hylaeochampsa vectiana was a small crocodyliform with endocranial adaptations suggesting a semi-aquatic lifestyle in a freshwater habitat.