This paper studies code-switching between Andalusian Arabic and Romance in the kharjas, the closing verses of the muwashshahaat poems. These poems, dating from the 11^th to the 14^th centuries, were composed in Classical Arabic, while the kharjas were written in two languages of Al-Andalus: Andalusian Arabic and Romance. The purpose is to investigate to what degree the structural aspect of code-switching in the kharjas conforms to descriptions in the current literature on code-switching in bilingual communities and what that tells us about the degree of bilingualism in Al-Andalus. The 43 kharjas (Corriente, 2008) present a total of 104 code-switches: 82 intra-sentential, 13 word-internal and 9 inter-sentential. The base language in the majority of cases is Romance: 73 % of the switches occurred from Romance to Arabic. Cross- tabulations of the direction of the switch, lexical category of the switched parts and what immediately precedes and follows them show statistically significant relationships, indicating that the code-switches found in this corpus are not the result of a random process of language mixing resulting in “an outlandish and deliberately unsophisticated patois” (Monroe, 1974:31). A study of the intra-sentential code-switches also contributes to an explanation of the behavior of the Arabic definite article, al- and its allomorphs, in Arabic loanwords.