Liquid effluent produced from tanning industries is loaded with organic and inorganic contaminants, particularly heavy metals, which may cause severe damage to the ecosystem. Constructed wetland (CW) is a promising product of the research in the field of ecological engineering which helps to overcome aquatic pollution. This investigation aims to develop a plant–endophyte synergism in CW for the efficient remediation of tannery effluent. In a vertical flow CW, Brachiaria mutica was vegetated and augmented with three endophytic bacterial strains. Results showed a reduction of 82% in COD, 94% in BOD5, and 95% in Cr by plant–endophyte synergism in CWs and it was significantly higher than the use of plants alone. Similarly, nutrients (N and P), lipids, ion content, SO42−, and Cl− showed similar reduction by the combined action of endophytes and B. mutica in CWs. The endophytes inoculation enhanced bacterial population in different compartments of the plants vegetated in CWs and the maximum was observed in the roots. This study revealed that plant–endophyte synergism in CWs can enhance the remediation of industrial wastewater.