The conducting polymer polypyrrole and polypyrrole/ZnO nanocomposites are synthesized by in situ polymerization method at 0°C–5°C temperature with ammonium persulphate as an oxidizing agent. The optical band gap of polypyrrole/ZnO nanocomposites have been studied at different weight percentage such as 10%, 30%, and 50%, at room temperature. The obtained absorption spectra in the wavelength range 200–800 nm by T90+ UV/Vis Spectrophotometer. The PXRD pattern confirmed the hexagonal wurtzite structure of the ZnO product. The particle size is calculated by using the Debye–Scherrer relation and it is found to be in the range of 20–50 nm. The absorption spectra at 385 nm obtained is the characteristic peak of ZnO and it is observed for all weight percentages of nanocomposites. Further, the peaks that occurred at 300and 469 nm (3.71 eV) confirm the formation of polypyrrole in nanocomposites. The optical properties of such conducting polymer nanocomposites are used in the field of optoelectronic devices and its wide band gap is useful in biomedical applications.