This research is a comparative-diachronic study of terms that appear in marriage certificates and that are related to the themes of marriage, divorce, separation, and property regime, since civil marriage was instituted in France (in 1791) and in Brazil (1890) until today. Its purpose is to verify which are the main challenges of certified translation that may be specifically linked to the evolution of these terms. The study arose from the following questions: is it possible to find different equivalents in a target language (TL) for the same term in a source language (SL) if terminological equivalence is conceived from a diachronic point of view? Does the terminological equivalence change from the diachronic point of view? If yes, what are the characteristics of this change? What are the main terminographic problems found regarding this subject? To answer these questions, the methodology adopted in this study consisted of five steps: i) four corpora were created, two of which were composed of French and Brazilian marriage certificates (respectively, FMCCorpus and BMCCopus) and the other two present laws and decrees relating to the above mentioned themes (FLCorpus and BLCorpus); ii) in the AntConc program (Anthony 2012), the terms in both languages were identified; iii) then, the semantic and lexical evolution of these terms was analyzed; iv) the FR-BR equivalents were established in the light of a diachronic perspective through the analysis of the concepts denominated by these terms in different moments of the history of the legal domain of these two countries. To follow this methodology, the theoretical assumptions of terminology (Cabré 1999, Conceição 1999, Alves 2006, and others) and diachronic terminology (DT) (Dury 1999, 2005 and 2013, Tartier 2006, among others) were adopted. As main results, it was found that there are terms that have different equivalents at different times of their existence in civil law (this is the case, for example, of divórcio that sometimes must be translated by séparation de corps, and other times by divorce), in addition to some situations in which equivalence has different degrees (Dubuc 2002) over time for the same pair of terms. It was also verified that the terminographic resources consulted do not provide the necessary data for a good understanding of these terms in relation to their dates of occurrence in legal documents, such as the marriage certificates of our corpora. Thus, the main challenges of certified translation in this context are especially linked to terminological transformations – the result of the evolution of specialized knowledge – and DT has proven to be a fertile field that highlights the semantic and lexical evolution of terminologies. Diachronic transformations are very relevant for translators, especially in the case of those who work with certified translations, as they can translate old documents in which the diachronic issues play a fundamental role. However, there is still a long way to go regarding the development of DT. Therefore, this communication proposes to present some reflections that can collaborate in this sense.