Urdu post positions need to be clearly defined because long as an accurate concept of Post position Phrases is chalked out, the concepts of Noun and Verb Phrase will also remain incomplete. The available literature describes them either semantically (traditional approach), or in Lexico-Functional-Grammar. Neither approach differentiates between their roles as case markers and post positions. Nor is their basic structure described. The researcher has tried to minimize the confusion between their mixed roles of case markers, grammatical functions, and post position.Disagreeing with the existing theory of Urdu PPs, the researcher has defined and classified them in the framework of generative grammar. This paper elaborates the internal structure of Urdu PPs, their maximal and intermediate projections, and their distribution in the clause structure. In addition to that, their overt and covert roles have also been pointed out here.