The influence of CuO incorporation on the structural, dielectric, and electrical properties of Na2O-SiO2-P2O5-Y2O3 glass-ceramics was investigated to assess their potential as solid-state electrolytes. Glasses containing 0-0.5 mol% CuO were synthesized and thermally treated to promote controlled crystallization. XRD and SEM confirmed the presence of CuSiO3 crystallites within an amorphous matrix. XPS, ESR, and optical absorption revealed the coexistence of Cu+ and Cu2+ ions, while Raman, IR, and PAL spectra indicated that Cu + ions occupy tetrahedral network sites and Cu2+ ions act as modifiers. The fraction of Cu+ ions increased with total CuO content. Dielectric and a.c. conductivity studies (frequency range: 4 Hz-8 MHz; temperature range: 310-633 K) indicated that higher CuO concentrations reduced both the dielectric constant and conductivity. This decrease is attributed to enhanced polaronic hopping and lower ionic mobility. While lower CuO compositions favored ionic conductivity and stability—making them suitable for electrolyte layers—higher CuO content promoted polaronic conduction, suggesting these glass-ceramics could also serve as electrodes in solid-state batteries.