This paper provides a contrastive study of the phenomenon of acronyms or “al-nāhat” in Spanish and Arabic. The study consists of four parts: an introduction to show the importance of the study, and three other parts. The first part deals with the origins of acronyms in the two languages. The second part is an analysis of the linguistic function of that phenomenon from the point of view of the Spanish and Arab linguists alike. The final part concerns the difficulties that the translator faces in translating this phenomenon. The main objective of this study is to reveal the common features of the phenomenon in the two languages and the possibility of translating it between them. Key words: acronyms, “al-nāht”, lexical creation, translatability.