In this study, we used the Pulsed Laser Ablation Technique (PLA) with varying ablation times to successfully synthesis Copper Iron Sulfide (CuFeS2) Nanoparticles (NPs) in diverse sizes. CuFeS2 NPs have a spherical structure with an average size of 17.9, 35.2, and 44.2 nm for ablation times of 15, 30, and 45 minutes, respectively, according to transmission electron microscopy (TEM) data. To display the distribution and percentage of each element in the sample, mapping and electron diffraction X-ray (EDX) were employed. The bonds between elements are confirmed using Fourier Transform InfraRed (FTIR) studies. The molecular structure, as well as the molecule's geometry and even symmetry, can be determined using Raman spectroscopy. The absorption peaks of CuFeS2 NPs exhibit a red shift as the ablation duration rises, according to the UV-Vis spectra. As the particle size grows, the associated band gap energy drops from 2.68 eV to 2.11 eV. A photoacoustic method (PA) was developed to evaluate the thermophysical parameters of CuFeS2 nanofluid. Thermal effusivity (e), the thermal diffusivity (α) and thermal conductivity (k) were obtained for the different samples using closed cell PA technique. The thermal conductivity of the samples increases from 0.636 to 0.9623 W/mK with the increase in the particle size from 17.9 nm to 44.2 nm.