In this work, 6-aminocaproic acid-modified copper ferrite nanoparticles were synthesized and used as an adsorbent for removing Amaranth dye from water. The modified nanoparticles were easily prepared using a simple and cost-effective method, namely the coprecipitation method. The nanocomposite was characterized by techniques like FTIR, XRD, SEM with EDS, and TEM. To evaluate the adsorption capacity of Amaranth dye, concentrations of Amaranth, contact time, nanocomposite dose, and solution pH were optimized. Further, Langmuir and the Freundlich isotherm models have been investigated. Among these, the Freundlich model showed the most accurate correlation with the experimental result, indicating a multilayer and physico-chemical adsorption of Amaranth dye onto the heterogeneous surface of the prepared nanocomposite. The Langmuir maximum adsorption capacity of this study was ~17 mg g⁻¹. Thermodynamic parameters (∆G° and ∆H°) confirmed that the adsorption process was spontaneous and exothermic. Adsorption kinetic studies showed pseudo second-order fitting with the multi-step adsorption process. The current adsorption performance was best for the first two adsorption–desorption cycles.