Morocco’s multilingual setting creates fertile ground for continuous language contact, particularly between Moroccan Arabic (MA) and Tashelhiyt Berber (TsB). This paper investigates the extent TsB’s influence on MA, identifying features in MA that are traced to sustained interaction with TsB. Although the two languages are distinct, their prolonged contact has led to systematic transfer. One reason is that TsB speakers learning MA bring their prior linguistic competence into the acquisition process. The analysis highlights four major domains of influence: lexical borrowing, morpho-phonological feature integration, syntactic restructuring, and semantic calquing. By situating the analysis within the broader framework of language contact, the study shows that TsB has had a profound and enduring effect on MA, underscoring that the foundations of Moroccan Arabic are rooted primarily in Berber rather than Literary Arabic.