In this study, parameters of the length–weight relation (LWR) were estimated for fifteen species of Gerreidae (mojarras) caught from the Pacific- and Atlantic coast of Mexico, including the Gulf of California. The Pacific species were: Diapterus aureolus,Diapterus brevirostris,Eucinostomus currani,Eucinostomus dowii,Eucinostomus entomelas,Eucinostomus gracilis,Eugerres axillaris,Eugerres lineatus,andGerres cinereus. The Atlantic species were:Diapterus auratus,Eucinostomus argenteus,Eucinostomus gula,Eucinostomus jonesi,Eucinostomus melanopterus, and Eugerres plumieri. The values of the exponent b of the length–weight relation ranged from 2.58 to 3.79. To the best of our knowledge, these are the first parameter estimates for nine species for the Mexican coast and for four on a worldwide scale.