This paper reports the degradation of indigo carmine and eosin Y dyes in water, catalyzed by cobalt and multiwalled carbon nanotube modified zirconium oxide nanocomposite (Co-ZrO2-MWCNTs) under si-mulated visible light. The bare ZrO2, ZrO2-MWCNTs, Co-ZrO2 and Co-ZrO2-MWCNTs with different per-centage compositions of cobalt were synthesized by homogeneous co-precipitation method. Character-ization of the prepared nanocomposites was carried out using X-Ray powder Diffraction (XRD), Fourier Transformer Infrared (FTIR) Spectroscopy, Transmission Electron Microscopy (TEM), Raman Spectro-scopy, (UV–Vis)-Spectroscopy and Energy Dispersive Spectroscopy (EDS) for their structure, formation, morphology, size and elemental analysis. The experimental results indicated that all the cobalt and MWCNTs modified nanocomposites demonstrated higher photocatalytic activities compared to the bare ZrO2. The most efficient catalyst (0.5%Co-ZrO2-MWCNTs) with the band gap and Ka values of 5.21 eV and 16.86 × 10-3 min-1 respectively exhibited 98% degradation efficiency toward indigo carmine and 87%toward eosin Y in 180 min.