Khorasani Kurmanji is one of the northwestern Iranian dialects that despite its proximity to many neighboring languages including Persian, Turkish, Arabic, Russian, and Armenian and loss of some morphological and syntactic features, has maintained one of the most distinguishing morphological and syntactic characteristics called ergative-absolutive case marking system. The initial state of this system includes the features that still remain in some Iranian dialects (such as Kurmanji, Talyshi, Tati, Baluchi, etc. ) while in others (such as the contemporary Persian, Central and South Kurdish, Lory, Mazandarani, Gilaki, etc. ), they have disappeared completely and have been replaced by other types of case-marking systems, including nominative-accusative. In this study, different case marking systems, particularly ergative-absolutive in Khorasani Kurmanji dialect, are studied at first, then its decay and conversion to other systems especially the horizontal one are also explored. Finally it is shown that this dialect has a split ergative case system.