The density functional theory (DFT)-based first-principles quantum mechanics calculations were utilised to generate structural, thermodynamic, and elastic data of face-centred cubic (FCC) binary Pt-W and Pt-Ta alloy compositions. All studied alloy compositions were confirmed to be formable and mechanically stable, with no indications of potential phase transitions. Both FCC Pt-W and Pt-Ta alloys exhibited remarkable mechanical properties, highlighting their potential for jewellery applications. The computed Poisson’s ratio (ν), Pugh’s ratio (k), and Cauchy Pressure (Cp) provided insights into the alloys’ ductility, which was found to decrease with increasing W and Ta concentrations. Conversely, hardness (HV) and elastic modulus exhibited significant improvements with higher W and Ta content. The increased hardness translates into superior wear resistance and durability, critical for preserving the aesthetic appeal and structural integrity of jewellery under prolonged use. Additionally, the remarkable elastic stiffness of these alloys enhances their suitability for jewellery applications, where attributes such as compressive spring power, rigidity, and elasticity are highly advantageous.