This paper investigates the internal structure of Construct State (CS) construction in Standard Arabic (SA) in an attempt to argue that genitive Case in this construction is structural. In Government and Binding (GB) theory, Chomsky (1981, 1986) distinguishes two types of Case: structural and inherent. He defines structural Case in terms of a structural relation between Case assigner and Case assignee, whereas inherent Case is defined in terms of a thematic relation between Case assigner and Case assignee. This distinction between structural and inherent Case is maintained in the Minimalist Program (MP). Chomsky (1986, 1995) argues that nominative and accusative Cases are structural, whereas genitive Case, whether prenominal or postnominal, is inherent. Chomsky's assumption that genitive Case is inherent has raised several problems. Alexiadou and Wilder (1998) and others such as, Roberts (1997), Sorin (2002), Jeong (2003), argue that prenominal genitive in English is structural. Their arguments are based on the similarities between prenominal genitives and clausal subjects which are structurally marked. In Hebrew, Siloni (1997) argues that genitive Case is structural. Likewise, Ouhalla (1991), Fehri (1993) and Kremers (2003) argue that genitive Case in SA is structural. Based on the main characteristics of CS construction in SA as well as nominalization, this study argues that genitive Case in Arabic CS construction is structural.