This paper focuses on investigating the null subjects in Hijazi Arabic and addresses how they are derived and interpreted. There is a strong connection between rich verbal agreement inflection and pro-drop in HA due to the language's highly inflectional nature. It is shown in this paper that HA is a consistent null subject language. This study is framed within Holmberg's (2005, 2010) theory of null subjects. Holmberg proposed that null subjects (henceforth NSs) are defective subject pronouns labeled Ps. The null subjects are derived via incorporation into T after the features valuation and union take place. The head T (a probe) has unvalued -features which are valued by the defective subject pronoun (a goal) and in return, the [u case] feature on P is valued by T. The incorporation of P into T forms a chain which is subject to chain reduction where the lower chain copy (the defective subject pronoun in spec-VP) receives a null spell out. The pronounced elements consist of the valued φ-features of T, which manifest as a verbal affix on the finite verb subsequent to the verb's incorporation into T. This reflects the deletion of the subject in spec-VP. The null subject is interpreted as a definite 3rd person null subject when the [uD(efiniteness)] feature of P is valued by an A-Topic (antecedent) in spec-TopP. On the other hand, it is interpreted as a definite 1st or 2nd person null subject if it is valued by speaker/addressee features in the domain of C (Complementizer).