Morphometric relationships (length–weight and fork length–total length) were estimated for four scombrid species (Thunnus tonggol, Euthynnus affinis, Cybiosarda elegans, and Rastrelliger kanagurta) that are of growing importance to fisheries, but are also important predators representing different trophic levels in the neritic regime of Australian waters. The sample of 1,137 fish representing a broad size range for each species produced highly significant model fits (r² > .95) that provide researchers with reliable information for future biological studies, stock assessment, and ecosystem models.