This study aims to find the optimal type and concentration of fibers necessary to reinforce and enhance the mechanical properties of asphalt concrete. Four types of fibers: polypropylene (PP) and polyester (Pe) fibers with a length of 6 mm, nylon (Ny) and carbon (C) fibers, all with a length of 12 mm, were incorporated into asphalt at 0.5% and 1.0% of volume content, respectively. Six test parameters were examined for each variable to investigate the influence of the fiber type and content: the Marshall stability, porosity, indirect tensile strength, moisture susceptibility, dynamic stability, and flexural performances. Furthermore, scanning electron microscopy (SEM) images were used to accurately analyze the test results. The test results show that most of the fiber-reinforced asphalt concretes provided significantly improved mechanical performances compared to the plain asphalt concrete specimen. The optimal fiber type was the Ny fiber for every test parameter, and the optimum volume content of the Ny fiber was 1.0%, except for the case of the dynamic stability.