Municipal solid waste contains large amounts of plastic and their utilization has environmental benefits including the reduction of raw materials used and landfill spaces. One of the possible uses of waste plastic is in construction applications such as partial replacement of coarse aggregate in concrete materials. In this paper, the structural capacity of reinforced concrete beams containing waste plastic was investigated. The waste plastic was the cap of a plastic bottle. Four concrete mixes were prepared. The coarse aggregate was replaced with 0, 10 %, 15 %, and 20 % (by volume) waste plastic. All mixes had constant mix proportions and water to cement ratio. All beams were cured for 28 days at 20 °C. The structural performance was assessed by examining the central deflection of the beam at different load increments until failure. In addition, the mode of failure was examined visually. The results indicated that it is possible to use a certain amount of waste plastic in structural applications without affecting the flexural characteristics of reinforced concrete beams.