Broadband near-infrared-II (NIR-II) covered phosphors are crucial for LED applications such as biological imaging and optical sensing. In this study, Ca5Ga6−xO14: xCr phosphors, where x represents the molar concentration of Cr4+ substituting Ga sites, were synthesized with x values of 0.0001, 0.0005, 0.005, 0.01, 0.02, 0.03, and 0.04 using a conventional solid-state reaction. X-ray diffraction showed that the main targeted phase was predominantly observed for Cr doping levels below x = 0.001. Optical characterizations revealed that the optimized phosphor (x = 0.0005) exhibited the most intense and broad NIR emission (1150–1600 nm, peak at 1330 nm) by 650 nm excitation, originating from the spin-allowed 3T2 → 3A2 transition of tetrahedrally coordinated Cr4+ ions. Low-temperature photoluminescence further elucidated the energetic and crystal field environment of Cr4+. These findings demonstrate that Ca5Ga6O14 is an efficient host for Cr4+-doped NIR-II phosphors, offering insights for the design of next-generation luminescent materials.