A study of the linguistic and grammatical activity during the Spanish colonial times in the Philippines shows that the missionaries decided to learn the vernaculars, rather than impose Spanish, in order to carry out their mandate of evangelizing the natives. The best known among these missionary grammarians was the Dominican Fr. Francisco Blancas de San José who wrote the Tagalog grammar Arte y reglas de la lengua tagala in 1610 for the use of his confreres. An analysis of the grammar reveals the author’s good mastery of the language and a description of specific linguistic features, which have preserved their validity to this day, despite the limited tools available to the grammarian at the time. Regardless of its imperfections, the Arte y reglas de la lengua tagala represents one of the first attempts at a description of Tagalog and provides contemporary linguists with a good starting point for modern and more accurate descriptions of the language