A novel pH-sensitive hydrogel was developed to use as a solid-phase extraction adsorbent for the removal of Cu(II) ions in aqueous medium. Adsorbent was prepared via free radical copolymerization reaction using 2-hydroxyethyl methacrylate (HEMA), acrylic acid (AA), ammonium acrylate (NH₄Ac), which was obtained by neutralization of AA with ammonium hydroxide, ethylene glycol dimethacrylate (EGDMA), and redox initiators (Na₂S₂O₈ / Na₂S₂O₅). FT-IR spectral analysis was performed for the structural and spectroscopic characterizations of the adsorbent. Effects of medium pH, adsorbent amount, initial Cu(II) concentration, contact time, and presence of a competitive ion, Ni(II), on adsorption capacity were investigated. Maximum adsorption capacity, 98.04 mg Cu(II)/g adsorbent, was achieved at pH 6.0. In addition, Freundlich and Langmuir isotherm equations were applied to predict adsorption behavior of Cu(II) ions on the synthesized adsorbent. Desorption, or recovery, studies were also performed using HCl at pH 1.25, resulting in 96.55% desorption level. Furthermore, reusability studies have proved that the adsorbent can be used at least 4 times without any remarkable loss in adsorption capacity. Since the adsorbent had high affinity for Cu(II) ions, it can be successfully used in the preconcentration and removal of trace amounts of Cu(II) ions in various media, including environmental and biological samples.