A novel single phased white light emitting phosphor Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂):Eu²⁺, Mn²⁺, Tb³⁺ was synthesized by solid-state reaction for the first time. The crystal structure, photoluminescence properties and the efficient energy transfer from different Eu²⁺ sites to Mn²⁺ and Tb³⁺ in Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂) is studied in detail by X-ray diffractometry Rietveld method, luminescence spectra, energy-transfer efficiency and lifetimes. Through effective energy transfer, the wavelength-tunable warm white light can be realized with superior chromaticity coordinates of (0.37, 0.30) and low correlated color temperature (CCT = 3512 K) by coupling the emission bands peaking at 410, 542 and 649 nm attributed to the contribution from Eu²⁺, Tb³⁺ and Mn²⁺, respectively. The results indicate the white phosphor Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂):Eu²⁺, Mn²⁺, Tb³⁺ can serve as a promising material for phosphor-converted warm white LEDs.