The photocatalytic degradation of toxic dyes has brought a new revolution to reduce water pollution. To degrade industrial dyes, TiO2 is an important photocatalyst but the role of morphology is also important in degradation. We have synthesized g-C3N4/TiO2 nanocomposite (1:1) having different shapes of TiO2 (nanorods (NR), nanospheres (NS), and nanotubes (NT)), to show the effect of morphology on its photocatalytic activity. To improve the photocatalytic efficiency of TiO2 in visible light, we have incorporated g-C3N4, a visible light active photocatalyst. The HRTEM, FESEM and Electron Diffraction studies with color mapping indicate successful synthesis of g-C3N4/TiO2 nanocomposites. The increased photocatalytic efficiency of the nanocomposites regarding the degradation of Rhodamine B (RhB) dye under visible light irradiation is due to the incorporation of g-C3N4 with different shapes of TiO2. The studies show that, the shape of TiO2 has a remarkable effect in photodegradation. The best degradation performance (similar to 97%) was obtained from g-C3N4/TiO2-nanotubes composite with a rate constant of 0.0403 min(-1) within 80 min, whereas degradation efficiency of other shapes of TiO2 like NS (92%) and NR (94.5%) were also found to be greater than that of commercial TiO2 (P25) composite (74%). Results from UV-Vis absorption study, X-ray Diffraction studies, X-ray photoelectron spectroscopy and BET analysis suggest that the improvement in photocatalytic activity of composite is due to increased light absorption in visible region and increase in surface area (137.1 m(2)/g). Results from different scavengers study (DMSO, ascorbic acid and methanol) indicate that electron and superoxide ions act as main reactive species in photodegradation of RhB dye. The reusability efficiency of the catalyst shows 86% degradation after 5 consecutive cycles. The effect of pH and catalyst concentration was also determined which shows that maximum degradation occurs at pH similar to 7 (98%) and degradation efficiency is increased with increase of catalyst dose from 0.1 mg/ml to 0.6 mg/ml and after that saturation occur due to increase in opacity and scattering of light. A comparative study was done with literature which suggests that this nanocomposites act as one of the best photocatalysts for degradation of toxic dyes. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.