Two neritic species of scombrids (Euthynnus affinis and E. lineatus) from the Indo-Pacific and the Eastern Pacific are today classed as commercially important. They have long been exploited and are common finds on coastal archaeological sites. Size reconstruction from isolated bones is interesting for both biologists and archaeologists. In archaeology, these studies make it possible to highlight fishing strategies. Therefore, we built an osteometric model for these two species, using 31 specimens of E. affinis (FL: 274 mm to 828 mm, W: 305 g to 8674 g) from the Sultanate of Oman and 26 specimens of E. lineatus (FL: 294 mm to 614 mm, W: 481 g to 4200 g) from Ecuador. For E. affinis, the length-weight relationship is W = 1E-05 FL3.0682, and for E. lineatus, the relationship is W = 2E-05 FL2.9578, with r2 higher than 0.98 for both species. For the osteometric model, we used the neurocranium, premaxilla, dentary, anguloarticular, quadrate, hyomandibula, maxilla, opercle, anterior and posterior ceratohyals, scapula and vertebrae. For each bone, we took between 2 and 5 measurements and plotted the obtained values against the fork length. For all selected bones, we produce at least one regression equation with a high r2 (> 0.9) that permits accurate estimates of the length and weight of Euthynnus individuals for both species.