Cadmium sulfide-graphitic carbon nitride nanocomposite was synthesized by pulsed laser ablation in liquid, and it was found from the results of optical and morphological characterizations that the proper anchoring of nanostructured cadmium sulfide on the nano-sheets of graphitic carbon nitride took place, which brought about the positive attributes such as enhanced visible light absorption and reduced photo-generated charge recombination, the key features required for an efficient photo-catalyst by solar light harvesting. The pulsed laser ablation in liquid method adopted for the synthesis of cadmium sulfide-graphitic carbon nitride has the following advantages: the shape and size of the synthesized particles can be controlled by altering the experimental parameters such as laser wavelength, pulse laser duration, the pH of the solution, the surfactants and the temperature of the solution, pulsed laser ablation in liquid method neither requires cumbersome equipment nor does it require intermediate chemicals and catalysts nor does it necessitate the post synthesis purification. The enhancement of photo-catalytic activity of cadmium sulfide-graphitic carbon nitride nanocomposite was tested for the photo-catalytic deactivation of Escherichia coli bacteria in water under visible light radiation. As anticipated, a significant improvement of photo-catalytic deactivation was observed, which is attributed to the enhanced and extended light absorption in the visible spectral region, and the formation of herterojunction between the semiconductors, which is instrumental in inhibiting the undesired recombination of photo-generated charge carriers. Quantitatively, the presence of cadmium sulfide on the graphitic carbon nitride surface contributed to a remarkable 129% increase of photo-catalytic degradation constant compared to pure graphitic carbon nitride, which resulted in the decrease of total depletion time of Escherichia coli from 156 min to 67 min with the cadmium sulfide-graphitic carbon nitride nanocomposite synthesized by pulsed laser ablation in liquid method. Our results on the efficient photo-catalytic deactivation of Escherichia coli under visible light assures that cadmium sulfide-graphitic carbon nitride nanocomposite can very well be used for photo-catalytic water purification by harvesting the abundant solar light.