Based on the number of specimens examined, review of reference collections and literature, we determined the presence of four cephalochordates (two genera and one family) in the seas of Mexico; moreover, the registry of the locations is denoted also a taxonomic key for their identification comes attached. The presence of three of the four species for the Gulf of Mexico and the Mexican Caribbean is registered, of which Branchiostoma caribaeum has the largest distributional area, from Veracruz coasts to the Yucatan Peninsula; B. longirostrum has been registered only on the west part of the Gulf of Mexico and Asymmetron lucayanum in front of the northeastern coast of Yucatan. Branchiostoma californiense is the only one registered on the Pacific coast of Mexico but it counts with a wider distribution.