: The cause of road pavement degradation can be traced to three factors of excessive traffic congestion or overload, poor materials, and adverse weather conditions. To achieve an economic and cost-effective road, road pavement should be built with the aim of achieving a long lifespan. This need for improvement of pavement performance and longevity has encouraged road engineers to modify the properties of bitumen and asphalt. Modified bitumen has generally better performance in terms of rutting, fatigue, reflective cracking, shrinkage cracking, frictional resistance and adhesion. Reinforcement of asphalt with fiber is a relatively new solution for improving the mechanical properties of asphalt concrete mixtures. Cost-effectiveness, good speed and ease of use, and improved physical and mechanical properties are some of the advantages of fiber reinforced bitumen over those reinforced with other materials such as polymers. Research has shown that adding fibers to bitumen as a modifier generally improves the asphalt performance and longevity. In addition, this can be counted as an environmentally friendly way of using waste fibers. The main objective of this study was to determine the adhesion of aggregates to fiber-reinforced bitumen. This objective was pursued through theoretical approach (modeling) and laboratory experimentation. In the theoretical part of work, a mechanical model based on the force balance theory and the theory of fiber slip in short-fiber reinforced composite materials were used to calculate the force required to pull-out aggregate from fiber reinforced bitumen. In the experimental part of work, 7.5-mm and 15-mm long polypropylene fibers, 15-mm and 30-mm long polyester fibers, and 15-mm long glass fibers were used to reinforce the bitumen 60-70. Three types of aggregate made of limestone, silica and slag materials were used for these experiments. In the next step, Instron tensile test machine was reconfigured for pull-out test. This test measured the force required to pull out pieces of aggregate from bitumen or fiber-reinforced bitumen under different conditions. Samples reinforced with polypropylene fiber and polyester fibers showed respectively 33% and 16% higher pull-out force than control samples. The best temperature range for mixing bitumen with polypropylene fibers was found to be 140-150°C, and the optimal duration of bitumen-polypropylene mixing was found to be 5 minutes. Samples made with silica aggregate achieved a higher pull-out force than those made with limestone or slag aggregates. For all samples, the pull-out force at temperature of 50°C was significantly lower than that at temperature of 25°C; adding polypropylene and polyester fibers to bitumen increased the pull-out force and adhesion at temperature of 50°C. Comparison of experimental and modeling results demonstrated the good ability of the model to predict the pull-out force. Fourier transform spectroscopy experiments were also performed to examine the relationship between bitumen and fibers strands. Keywords: fiber-reinforced bitumen, fiber, polypropylene, polyester, glass, pull-out test, Fourier transform spectroscopy, mechanical model