The present study aims at investigating and contrasting the use of modal verbs in the writing of Brazilian undergraduates majoring in English as a foreign language (EFL), contrasting it to that of British and American university students who speak English as a first language. To this end, it makes use of both the theoretical background of Corpus Linguistics (Sinclair, 1991; McEnery & Wilson, 1996; Hunston, 2002; Berber Sardinha, 2004; McEnery, Xiao & Tono, 2006) and of technological resources, especially the computer program WordSmith Tools (Scott, 1999), to analyze two corpora. The research corpus consists of a section of the Br-ICLE (The Brazilian Portuguese Sub-corpus of the International Corpus of Learner English) which has been collected in four universities in the city of Rio de Janeiro, totaling 51,430 words, while the reference one corresponds to a part of the LOCNESS (Louvain Corpus of Native English Essays), accounting for 165,135 words. Adopting a textual approach to writing (Hyland, 2002) and using statistical tests to quantify the results, the investigation focuses on central modal verbs (Biber et al., 1999), namely, can, could, may, might, must, shall, should, will and would. Results indicate that the Brazilian speakers of English make less use of modal verbs than their American and British counterparts. More specifically, it is observed that both will and would present significantly lower frequencies in Brazilian EFL writing. Differences among modals are also found when the patterns of use of these verbs are taken into account. Research results show that there are certain differences in the written production of the two groups, which may contribute to the teaching of English in the Brazilian context.