Natural fiber-based polymeric composites have become increasingly popular in machine tool and automobile applications in recent years. While, using the composite in such applications, it may fail due to excessive vibrations caused by dynamic loads. Therefore, it is necessary to understand the free vibration behavior of composites before employing it to such applications. The purpose of this work is to compare the free vibration characteristics of untreated and sodium bicarbonate treated Phoenix sp. fiber reinforced polyester composites fabricated through compression molding technique with different fiber content (0, 10, 20, 30 and 40 wt.%) and constant fiber length (20 mm). The chemical treatment was carried out for different time periods (24, 120 and 240 h) with 10 wt.% concentration of sodium bicarbonate solution. The results revealed that the natural frequency of treated fiber composites was greater than the untreated fiber composites which maybe ascribed to the increased stiffness of the fibers and interfacial bonding after the treatment. In addition to this single fiber pull-out test was also performed to assess the interfacial strength among the composite constituents. Especially, the composites loaded with 120 h treated fiber showed better results and it can be suggested for various engineering applications.