Concrete mixed with coconut fiber waste is an innovation in using waste as an effort to support sustainable development. Meanwhile, there has been a lot of research related to concrete mixed with coconut fiber, but there is still very limited research on coconut fiber concrete that has been corroded. Therefore, this study aims to evaluate the mechanical properties of corroded reinforced concrete with variations in coconut fiber of 0.25%, 0.5%, 0.75%, and 1% of the weight of cement. The specimens used were 10 concrete beams with dimensions of 100 x 100 x 500 mm with a mixture of coconut fiber and a corrosion level of 5%. The corrosion acceleration process uses the impressed current method and flexural strength testing using a single-point loading method in the middle of the span. The results show that the flexural strength value of concrete increases with the addition of the percentage of coconut fiber, resulting in a concrete variation of 0.75%. However, the trend of the flexural strength value is inversely proportional to the trend of the resulting density value because the coconut fiber is not evenly distributed when making the specimen.