<p>High-quality lighting and agricultural supplementary lighting are both limited by the shortage of efficient red-emitting phosphors for white light-emitting diodes. To address this limitation, a series of dual-doped KSr₆ScSi₄O₁₆:5&#xa0;mol% Ce³⁺,<i> y</i> Mn²⁺ (0 ≤ <i>y</i> ≤ 25&#xa0;mol%) phosphors were successfully synthesized via a high-temperature solid-state reaction under a reducing atmosphere. Comprehensive photoluminescence characterization reveals that the co-doped samples exhibit dual-emission features under ultraviolet excitation, comprising an intense blue band centered at 407&#xa0;nm originating from the allowed 4<i>f</i>-5d transition of Ce³⁺ and a deep red band at 660&#xa0;nm attributed to the forbidden ⁴T₁(⁴G) → ⁶A₁(⁶S) transition of Mn²⁺. The energy transfer process from Ce³⁺ to Mn²⁺ was systematically investigated, demonstrating a markedly high energy transfer efficiency of 74.74% at the optimal Mn²⁺ concentration of 25&#xa0;mol%. The KSr₆ScSi₄O₁₆:5&#xa0;mol% Ce³⁺, 2&#xa0;mol%Mn²⁺ phosphor exhibits exceptional thermal stability, retaining 58.18% of its room temperature luminescence intensity at 420&#xa0;K. The as-prepared WLED device demonstrates outstanding performance with a color rendering index (<i>R</i>_a) of 84.6 and a correlated color temperature (CCT) of 5956&#xa0;K. The dual blue-red emission renders this phosphor promising for high-performance solid-state lighting, and its tunable blue/red intensity also endows it with great potential for plant growth supplementary lighting.</p>