The abundance of the wiskered sole Monochirus hispidus in the Sado Estuary showed a marked seasonal pattern, the highest densities occurred in spring and summer. The density of this species was mainly related, non‐linearly, to depth, water transparency and percentage of gravel, fine sand and mud in the sediment. Monochirus hispidus fed mainly on crustaceans and polychaets. Significant differences were found between the proportions of prey items eaten and total length class; larger fish consumed more decapods and polychaets. The von Bertalanffy growth equation coefficients differed between sexes. The asymptotic length L∞ obtained for females was higher compared to males, while the growth coefficient (K) was higher for males. Individuals with mature gonads were found between March and September, but the main spawning period of M. hispidus in the Sado Estuary was from March to June.