The braincase of Leptopleuron lacertinum Owen, a leptopleuronine procolophonid from the Late Triassic (lower Norian) of Scotland, is described for the first time. Morphologically, the braincase of Leptopleuron is similar to that of the Early Triassic genus Procolophon, and to a number of other procolophonids currently included in the subfamily Procolophoninae Romer, 1956. Several features of the braincase of Leptopleuron are derived within the Procolophonidae, but others are unique to this genus. Apomorphies include a strongly tripartite occipital condyle, a metotic foramen that is not walled by bone anteriorly, an ‘ascending process’ of the basisphenoid that forms a robust flat-ended expansion, and bears ventrally a thin laterally directed lamella, a ‘processus infrastapedialis columellae’ of the stapes that is aligned with the long axis of the footplate, loss of the foramen for nerve IX on the ventral ramus of the opisthotic, and a greatly expanded, vertical basisphenoid rostrum. These features may be autapomorphic for Leptopleuron, or represent synapomorphies of the Leptopleuroninae Ivakhnenko, 1979.