Ductile behavior is one of the most important earthquake indicators that must be possessed by structures. Because of the limited tensile strength of concrete, alternative materials such as structural nanosynthetic fibers as three-dimensional reinforcement bars have gained increasing popularity over several decades. However, the contribution of fibers to the development length of reinforcement bars has not been investigated. Therefore, an experimental study was conducted to investigate the effects of polypropylene fibers on the development lengths of reinforcement bars. Thirty-three reinforced concrete (RC) slabs at three different volume fractions of fibers of 0.0, 1.0 and 1.5 % at different embedment lengths of reinforcement bars were investigated under four- point flexural strength tests. Load-displacement curves, energy absorption capacities, ductility ratios and bond-slip relationships were obtained for different embedment lengths of reinforce-ment bars with three different amounts of fibers in RC concrete slabs. The test results revealed that the predominant effects of fibers on structural behavior pertained to the energy absorption capacities at plastic deformation. It was found that resisting more strains by reinforcement bars with the help of added polypropylene fibers resulted in the regaining of ductile behavior due to the reduced embedment lengths of the reinforcement bars.