Eco-friendly concrete is the most recommended sustainable option to reduce the excessive diminution of concrete natural resources and the high generation of greenhouse gas emissions. Therefore, the present study explores the feasibility of employing treated wastewater (TWW), recycled concrete aggregates (RCA), and fly ash (FA) in concrete mixes. A total of 4 reinforced concrete (RC) beams were investigated under 4-point bending setup with three parameters investigated; namely, mixing water (fresh water and TWW), coarse aggregates (gabbro and RCA), and cementitious binders (cement and FA). The experimental results revealed that the beams' ductility was decreased by 9% and 16% with TWW and RCA, respectively. Moreover, the flexural performance of the TWW-RC beams was decreased by 14%, whereas RCA-RC beams showed comparable flexural strength to its counterpart with natural aggregates. In addition, the utilization of FA at a 20% replacement ratio enhanced the flexural strength by 5% to 7%.