The stuccos of Imamzadeh Abdollah in Arak are Iranian-Islamic motifs common in Seljuk era and influenced by the Sassanid period. The study has been conducted by an analytico-descriptive and comparative methodology and the data have been collected through library research and survey. The study attempts to provide answers to the questions in that to what extent the art of Islamic stuccos are indebted to the Sassanid period and how the underwent changes on the Islamic stuccos are determined. The results indicate that the foundation of decorating stuccos has been influenced by the stuccos of the Sassanid period and their motifs’ contents have been inspired by divine teachings and important social events (translation movements and tendency to rationalism); accordingly, four kinds of changes (eliminating human and animal motifs, having tendency toward plant and abstract motifs with a mythological view on them, applying inscriptional motifs, and proposing polygonal geometrical motifs) could be observed in the themes of the stuccos’ motifs of the Imamzadeh.