<p>Barium titanate (BaTiO₃, BT) is a promising lead-free ferroelectric, but its sharp phase transition and temperature-dependent dielectric properties restrict its practical use. To overcome these limitations, Ba₁₋₃ₓNd₂ₓTi₁₋_yZr_yO₃ ceramics (x = 0.025; y = 0–0.125) were synthesized to explore the combined effects of Nd³⁺ substitution at the A-site and Zr⁴⁺ substitution at the B-site. XRD confirmed the perovskite phase formation with a tetragonal–pseudocubic (nearly cubic, but with very small hidden distortion) transition as Zr content increases to 0.05 (BT3) and the pseudocubic transition continued up to 0.125 Zr content (BT6). Nd doping introduced the lattice distortion and reduced leakage by suppressing oxygen vacancy formation, while Zr substitution expanded the unit cell and broadened the ferroelectric–paraelectric transition, yielding relaxor-type behavior (means a material that shows diffuse, frequency-dependent ferroelectric behavior instead of a sharp, normal phase transition). The P–E hysteresis analysis confirms that the ferroelectric nature of BaTiO₃ progressively transforms into a relaxor-type behavior with increasing Zr content. The composition BT3 (x = 0.025, y = 0.05) exhibits the optimal balance of ferroelectric and electrical properties, showing moderate polarization, high insulation resistance, and excellent temperature-stable dielectric performance. Dielectric studies showed enhanced permittivity, reduced loss, and improved thermal stability in co-doped samples. Electrical analyses indicated increased resistivity and suppressed conductivity. Overall, Nd–Zr co-doping effectively tunes structure and properties, enabling multifunctional BaTiO₃ ceramics for capacitors, sensors, and energy storage devices.</p>