Vertebrate gills may be either external (protruding from the body surface) or internal (enclosed in a chamber). Among living amphibians, external gills are found in salamander larvae and neotenes, early frog larvae, and caecilian embryos; internal gills are found only in later-stage frog larvae. Evidence for internal gills has also been found in stem tetrapods, and amphibian-like external gills have been found in some fossil temnospondyls and anthracosaurs. Gill homology among these groups and life stages has long been questioned. To address this, we used scanning electron microscopy, vascular casting, and paraffin sectioning to study the morphology of gills and associated vessels of three sarcopterygian species: the basal frog Ascaphus truei, the salamander Dicamptodon tenebrosus, and the lungfish Lepidosiren paradoxa. In all three species, blood flows from the heart through four pairs of afferent branchial arteries, through the gill lamellae, and drains through efferent branchial arteries into the dorsal aorta. In D. tenebrosus and A. truei no gill lamellae are found on the fourth branchial arch; instead, the afferent branchial artery supplies blood to the lung. In the external gill of D. tenebrosus the afferent arteries travel posterolaterally within an elongation of the septum and protrude dorsolaterally from the body, supplying blood to the paired, digit-like lamellae via a single vascular loop per lamella. A. truei, unlike most anuran larvae, never develops external gills, but only internal gills. These extend directly from the ventral side of the branchial arches. Each lamella has multiple club-like branches, each housing a vascular loop. These findings shed light on the morphology and evolution of sarcopterygian gills.