<p>The aquatic ecosystem is contaminated by the increasing amounts of residual dye wastes that are released as a result of the extensive use and large-scale production. As such, innovative and affordable technologies are necessary for minimizing the issues caused by dye waste pollution. Bimetallic nanoparticles are emerging as the preferred nanocatalysts for the efficient degradation of these residual dyes into less harmful intermediate molecules. Herein, monodisperse ruthenium-gold bimetallic nanocrystals (Ru-AuNCs) are synthesized under various synthetic conditions using octadecylamine (ODA) for the photo-Fenton catalytic degradation of indigo carmine (IC). The structural and optical properties were investigated using TEM, XRD, TGA, FTIR, XPS, and UV-vis spectroscopy. The TEM analysis revealed that the obtained nanocrystals were highly monodispersed, characterized by uniform size and shape, with an average particle size of 8.49 ± 1.07&#xa0;nm. The photo-Fenton process demonstrated a significantly higher degradation efficiency of 98% compared to the Fenton process, which achieved a degradation of 47%, respectively. The enhancement in photo-Fenton performance was attributed to the combined photo- and Fenton-like catalytic processes in the presence of hydrogen peroxide (H₂O₂) as oxidant. The Ru-AuNC catalyst maintained its stability even after four reuse cycles. The IC degradation mechanism of the photo-Fenton catalytic process was also proposed. Moreover, in vitro toxicity assessment of the degradation byproducts indicated that the products of the photo-Fenton process resulted in small molecules with no hazardous effects on human HEK 293 and CACO-2 cells. These results present Ru-AuNC as promising materials, offering a reliable and efficient degradation pathway for organic dyes with negligible toxicity.</p>