The arrival of Islam in Khorasan and change of the function of some buildings and establishment of new building complexes did not mean the collapse of the intellectual and artistic structures of pre-Islamic Khorasan and Iran. What the Sasanian artists had experienced in creating intellectual and artistic innovations and illustrated in the form of stucco decorations and paintings on the walls of palaces and temples established the essential bases for Islamic art in execution of architectural decorations. The Khorasanian Muslim artists followed up the same Sasanian style not only in the technics and methods but also in the form and artistic combination of their creations and amalgamated the pre-Islamic traditions with the new cultural trends including geometry and Islamic ideologies. Thus, a new perspective was created in producing the Islamic-architectural decorations of Khorasan that were influenced by the pre-Islamic artistic tradition on the one hand and brought up an innovative and updated style by adopting newly-emerged trends in thoughts and ideology of the Islamic period on the other hand. With an analytical-comparative approach, this paper addresses the role of the Sasanian artistic tradition in the definition of the architectural decorations of Khorasan during the first 6 centuries of the Islamic period.