The overall aim of this study is to identify the developmental stages of Arabic Nominal and Verbal structures. The study presents a systematic analysis of specific Arabic structures and tests learners’ inter-language development in real time. It describes the relationship and internal information exchange within Arabic Nominal and Verbal structures. The study tests Processability Theory (Pienemann 1998; 2005) predictions for agreement morphology in the acquisition of Arabic L2. Students of Arabic language and applied linguistics may use specific parts of this study as a reference to gain a better understanding of Arabic language syntax and morphology. In addition this study is a useful tool that presents a thorough description of language development (Arabic L2), and helps teachers and researchers to develop effective teaching materials and syllabus.