This paper investigates the lexical immigration of “arabismos” (Arabic loanwords) in the Spanish language. It compares the differences between old arabismos (integrated during the Middle Ages) and modern arabismos (integrated in contemporary time) in terms of their adaptation to the Spanish norms of spelling, phonetics, semantics and morphosyntactic. It also analyses the use of the arabismos and their immigration process during their first phase of presence in the written Spanish language (or predecessor language to Spanish). Through the study of a corpus collected from the databases of the Royal Spanish Academy (RAE), this paper has come to conclude that the anticipated differences between the two types of arabismos has been affirmed, and that the loss of adaption of the modern arabismos to the Spanish linguistic patterns has resulted in a maintenance of them as foreignisms.