The development of the Siculo Arabic group of varieties in the early medieval period took place at a time when Sicily was a cross-road of two major cultures, the Latin and the Byzantine. Palermo was a melting pot of linguistic contacts - Romance, Greek and Arabic. The question of language use in Sicily under both the Islamic (213-485/827-1091) and the Norman (485-681/1091-1282) is a complex one. The Arabic spoken by Arabs and non-Arabs at different layers or registers was a different variety to the highly archaized form of Classical Arabic. This study contributes to the understanding of Siculo Arabic in that (i) it re-examines in some detail traditionally accepted theories in the light of primary Arabic and secondary sources; (ii) it re-evaluates the linguistic situation in Sicily and it reveals that the Arabic of Sicily was not confined to one variety but several, which can be phonologically, and in some cases morphologically reconstructed; (iii) it establishes for the first time a possible link between the Siculo Arabic group and Medieval Maltese. The wider view of this is that Maltese emerged from Siculo Arabic directly rather than as was always believed from North Africa; and (iv) in the area of comparative dialectology, it adds to our knowledge common phonological features shared with Andalusi Arabic. Until now, scant attention has been given by dialectologists to the dialects of Arabic in Sicily. This much-needed study draws together the linguistic data covering the Arab and post-Arab period and illuminates the diversity and complexity of the dialects in Sicily.