In this study, a naked-eye colorimetric sensor was fabricated based on a Schiff base (–SH) derivative immobilized onto polyvinyl alcohol (PVA) microspheres. The surface morphology of PVA-SH was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The PVA-SH microspheres could selectively detect Cu²⁺ by a visible color change. This novel chemosensor demonstrated high sensitivity and selectivity for the detection of Cu²⁺, which can induce a color change of PVA-SH from white to yellow. PVA-SH exhibited a detection limit of 0.086 μM for Cu²⁺. Moreover, this simple and cost-efficient chemosensor was used for detecting Cu²⁺ in actual environmental water samples.