[3] Callinectes similis is most closely related to Callinectes danae,[4] a species also found in the Gulf of Mexico, but whose range extends as far south as Rio Grande do Sul,[5] and C. ornatus, a species found from North Carolina to Rio Grande do Sul.

[7] It can be told apart from the more distantly related C. sapidus by the number of teeth on the front edge of the carapace, there being six in C. similis and only four in C.

[7] Callinectes similis is found in the Western Atlantic Ocean, Caribbean Sea and Gulf of Mexico from the United States to Colombia.

[3] There has been considerable confusion between the various species of Callinectes, and it now appears that all individuals reported as C. danae and C. ornatus from the Gulf of Mexico (with the exception of parts of Florida) are actually C.

[2] Spawning takes place in the spring and fall, with females returning to estuaries to release their eggs.