This paper investigates the syntax of the null pro subject in Early Modern English, Standard Arabic and Modern Standard English and points out how the pro-drop parameter works in these languages. The objective is to show how in languages with rich agreement inflection like Early Modern English and Standard Arabic, the null pro is allowed in the structural subject position of finite clauses, whereas in languages with poor agreement morphology like Modern Standard English it is not permitted. It further illustrates that the rich AGR inflections in Early Modern English and Standard Arabic serve to identify the null pro subject, since the feature-content of the latter (i.e. the pro) can be recovered from the AGR morpheme on the verb morphology. Following Chomsky‟s (1995) minimalist analysis, I show how the nominative Case and agreement features of the (pro) subject are licensed and how the tense features of the verb are checked in Early Modern English and Standard Arabic. Furthermore, I present an alternative analysis which accounts for the occurrence of the null pro in finite clauses of Standard Arabic. I assume that the D-feature of I(NFL) is strong in the VSO and SVO structures with null pro subjects in Standard Arabic.