<p>A simple wet chemical technique is employed to synthesize covellite (CuS) nanostructures having localized surface plasmon resonance absorption in the near-infrared (NIR) region. Nanostructures having varied morphologies are synthesized by varying the synthesis time to get control over the line shape of the plasmon resonance absorption spectra. The optical properties of CuS nanostructures are found to vary significantly with the varied morphologies. The photothermal effect of these nanostructures is observed using a low-cost, easily available NIR light, having a broad emission spectrum over the NIR range, rather than laser light, which emits light of a single, particular wavelength. The experiment is fashioned in that way so that the maximum wavelength range of NIR absorption peaks can be utilized for photothermal conversion. The heat conversion efficiencies are found to rise gradually from 72 to 82% for the samples prepared with increasing synthesis time. The maximum temperature change and heat conversion efficiencies are registered for the sample that corresponds to the highest synthesis time in the present study. The straightforward approach used in this study allows the synthesis of assembly of undoped CuS nanostructures with controllable surface plasmon resonance and exceptional heat conversion efficiencies. These CuS nanostructures can be employed in medicine to stimulate cancer cell proliferation in the presence of NIR light.</p>