Synthesis of unique morphologies in photocatalytic materials, coupled with utilization of wide-spectrum solar energy through rare earth doping, holds significant promise to maximize the potential of photocatalysts. Herein in, cube-like Holmium (Ho) doped Bi5Nb3O15 was synthesized by the hydrothermal method and integrated with reduced graphene oxide (rGO) sheets. As synthesized Ho-Bi5Nb3O15@rGO composite along its analogs i.e., Bi5Nb3O15 and Ho-Bi5Nb3O15 was characterized by XRD, SEM, FT-IR, TGA, I-V, EIS, Mott-Schottky and photo-current measurements. Phase studies showed that crystallite size for Bi5Nb3O15, Ho-Bi5Nb3O15, and Ho-Bi5Nb3O15@rGO was 27.4, 25.5, and 13.5 nm, respectively. Optical analysis exhibited a reduction in the band gap in consequent to Ho doping from 2.54 to 2.19 eV for Ho-Bi5Nb3O15. Conductivity and photo-current measurements showed a remarkable increase in both electrical conductivity and photo-response of Ho-Bi5Nb3O15 upon its incorporation into rGO matrix, reaching maximum values of 1.72 × 10-2 S/m and 0.66 μA, respectively. The enhanced photocatalytic activity of Ho-Bi5Nb3O15@rGO was ensured through the outstanding photo-degradation efficiency (96.5%) against crystal violet (CV), greater than Bi5Nb3O15 (49%) and Ho-Bi5Nb3O15 (63.4%). Additionally, Ho-Bi5Nb3O15@rGO showed sufficient potential towards the degradation of acetylsalicylic acid (ASA) with 79.1% photo-degradation. This elevated photocatalytic activity of Ho-Bi5Nb3O15@rGO is believed to be contributed by the collaborative outcomes aroused from the Ho-doping and heterojunction fabrication among cubical Ho-Bi5Nb3O15 and rGO sheets. Hence, our work proposes an efficient strategy for the development of innovative photolytic materials for sustainable wastewater remediation.