The low thermal conductivity of conventional fluids like water poses a significant challenge in heat transfer applications. In this study, iron oxide (Fe₃O₄) nanoparticles were synthesized using the co-precipitation method with precise size control. Two samples were prepared by adjusting the pH with NH₄OH (Sample 1: 29.42 nm) and NaOH (Sample 2: 38.04 nm). Characterization using XRD, SEM, and TEM confirmed cubic-phase Fe₃O₄ with spherical morphology. Stable nanofluids were prepared using Arabic gum as a stabilizing agent, achieving zeta potential values of -31.7 and -35.2 mV. Critical Heat Flux (CHF) analysis revealed that Sample 1 showed a 2.7% increase in CHF at 620 kg/m²s, outperforming Sample 2 (1.6% improvement). The Nusselt number for Sample 1 increased by 4.5% at 920 kg/m²s. These results demonstrate that smaller nanoparticle size (29.42 nm) significantly enhances heat transfer efficiency. These findings highlight the potential of Fe₃O₄ nanofluids for industrial applications, including energy systems, automotive cooling, and electronic thermal management, where improved heat transfer efficiency is critical.