A large part of the morphology of Beja, the sole language of the Northern branch of Cushitic (Afroasiatic), belongs to the root and pattern system. This system is typologically similar to the Semitic one (particularly robust in Arabic) and is also found to a lesser extent in two neighboring Cushitic languages, Afar and Saho, but not in any other Cushitic language. This paper reviews the different patterns of the Beja morphological system, and compares them with the systems of its main Semitic contact language (Arabic) and with other Cushitic languages (Afar and Saho). No clear case of borrowing, copying, or replication from dominant and prestigious Arabic could be found, but sociolinguistic and linguistic data favors an interpretation in terms of a convergence phenomenon. The paper argues that contact with Arabic was a strong factor for the preservation of a crosslinguistically uncommon system in a large part of the Beja morphology. It also argues that intensive language contact between genetically related languages may help to preserve a morphological system which otherwise would have disappeared as is the case in most other Cushitic languages.