This work is an updated checklist of Mexican Pycnogonida species for both oceans, the Mexican Pacific (PA) and the Gulf of Mexico (GMx). This research was carried out based on the first historical records by Schimkewitsch in 1893 up to the present day. The number of recorded species increased in this study. The total number of species in Mexican oceans is 58, distributed among 19 genera and 10 families. All records were cross-referenced with the original literature, and those found to be questionable were deleted from the checklist. With the data reported in this checklist, an extrapolation of the total number of species was performed using rarefaction curves, thus demonstrating that the recorded species fell well below the projected diversity. The curves showed an estimate of 80 species in the Pacific, whilst 100 species were projected for the Gulf of Mexico. These data indicate that collection efforts and species occurrences nationwide and by waterbody (PA and GMx) are insufficient to describe the diversity of Mexican pycnogonids.