Composites of polyaniline (PANI) and cadmium sulfide nanoparticles (CdS NPs) are in situ synthesized by polymerizing aniline in acetic acid medium for different concentrations of CdS NPs. The composites, characterized by scanning and transmission electron microscopy, exhibit nanotubular morphology of PANI decorated with nanospheres of CdS NPs at their outer surface. The FTIR and UV-vis spectra indicate strong interaction between PANI and the CdS NPs suggesting a good conjugate for photovoltaic applications. The dc conductivities of the composite increase with an increase of the CdS concentration showing a maximum of 1.17 × 10⁻² S cm⁻¹ for the C200 sample (obtained by polymerizing 182 μL aniline with 200 mg CdS). The current–voltage plots indicate that the photocurrent is higher from the dark current and the separation between the dark current and photocurrent is maximum in C200. The effectiveness of these composites in DSSCs is studied under illumination of 100 mW cm⁻² and the C200 device exhibits a maximum open circuit voltage of 0.73 V, a short circuit current of 8.22 mA cm⁻², and a power conversion efficiency of 3.96%. The impedance study of the cells indicates that the lifetime of the photo-injected electrons is highest (1.34 ms) for the C200 sample, explaining the maximum PCE among the composites.