The base course is an essential component in a flexible pavement which supports the surface course and distributes traffic loads to the subbase and subgrade. Asphalt treatment has been widely used on granular base course material to enhance the material's properties and overcome its deficiencies. However, a comprehensive evaluation on the performance of flexible pavements with different asphalt-treated base materials has not been done yet in the literature. In this study, the AASHTOware Pavement Mechanistic-Empirical (ME) Design software and Alaska Flexible Pavement Design (AKFPD) program were used to predict the performance of flexible pavements with four different ATBs, i.e., hot asphalt-treated base (HATB), emulsified asphalt-treated base (EATB), and foamed asphalt-treated base (FATB), and reclaimed asphalt-pavement-treated base (RAP-TB), and one control granular base. The International Roughness Index (IRI), rutting, and fatigue cracking of flexible pavements with different base materials were predicted and compared. The structure number (SN) of pavements (with the same pavement structures) with different base materials was calculated and compared. The results indicated that pavements constructed with ATBs or RAP-TB can have similar or better performance than those constructed with granular base.