Global environmental problems are one of the biggest threats to humanity today. These problems include water contamination, which is made worse by the economy's and industry's rapid growth. We describe in this work a new method for synthesis of ZrMo₂O₈ nanoparticles (NPs) by employing a phosphomolybdic acid (PMA)-modified zirconium ceftriaxone complex as a precursor. The precursor was thermally decomposed for 2 h at 600 °C, producing ZrMo₂O₈ NPs. Using transmission electron microscopy (TEM) and X-ray diffraction (XRD), the structural and morphological characteristics of the produced NPs were described. ZrMo₂O₈ NPs had a dense spherical structure with an average diameter of 25.2 nm. The surface characteristics of the modified complex and the resulting ZrMo₂O₈ NPs were investigated via nitrogen adsorption-desorption. Their specific surface areas were determined using the BET method to be 22.4 m²/g and 21.7 m²/g, respectively. Remarkably, ZrMo₂O₈ NPs showed a greater pore volume of 0.041 cm³/g and a larger pore width of 2.26 nm. Conversely, the modified complex had a pore volume of 0.023 cm³/g and a pore width of 2.06 nm. The adsorption efficiency of the ZrMo₂O₈ NPs was tested for the removal of Rhodamine B dye (RhB) from aqueous solutions. The adsorption studies indicated that the ZrMo₂O₈ NPs (50 mg) show rapid RhB adsorption (50 mL of 5.0 ppm), 95 % removal efficiency was attained in 180 min at pH 7. The highest adsorption capacity of 9.5 mg/g was observed when using 15 mg of ZrMo₂O₈ and 50 mL of 10.0 ppm RhB dye at pH 7. The studies of linear and non-linear kinetics showed that the adsorption mechanism is best described by pseudo-second-order model. The reusability of ZrMo₂O₈ NPs was examined over several cycles. Only a slight decrease in removal efficiency was observed, with removal efficacy reached 90 % after four cycles. Our results showed that the PMA-modified zirconium ceftriaxone complex is an effective precursor for producing ZrMo₂O₈ NPs. Furthermore, the nanoparticles are highly efficient adsorbents for the dye removal applications.