The Colegio de Santa Cruz de Tlatelolco, established in 1536, liberally educated the sons of Nahua (Aztec) leaders in New Spain. Its Franciscan pedagogues, including Bernardino de Sahagún ( c . 1499–1590), Andrés de Olmos (1491–1571) and Juan Bautista ( c . 1555–1606/13), worked with indigenous students and alumni to collect, edit and circulate Nahuatl huehuetlahtolli , or ‘speech of the ancients’. This paper examines the largest collection of these orations printed in pre-modern Mexico, the Huehuetlahtolli  edited by Juan Bautista and indigenous intellectuals from the college. It argues that the Tlatelolcans adapted Nahuatl ‘old words’ for the New World of colonial society. They ornamented the speeches with rhetorical techniques derived from Santa Cruz's Erasmian curriculum. They interpolated biblical sentences, particularly from Proverbs and Sirach, to enhance the evangelising potential of the discourses. Finally, they drew on Erasmus's theory of speech, as expressed in his pedagogical and spiritual writings, to explicate Nahuatl los difrasismos concerning eloquence and good counsel. Contextualising the Huehuetlahtolli  in Santa Cruz's Erasmian schoolroom reveals the contours of its argument for vernacular evangelisation, the liberal education of indigenous youth and for the elegance of the Nahuatl tongue.