While there are several vocabularies of indigenous languages in Mexico, including one of Seri called “comcáac” by its speakers, the production of dictionaries is very limited. Therefore, the work compiled by Mary Beck Moser and Stephen Marlett is a real breakthrough for the least explored areas of linguistics devoted to the native languages of Mexico and on the indigenous languages spoken throughout the world. On this article we will focus on the Seri – Spanish part of the dictionary mentioned above.