Display omitted •A blue-LED-excitable NIR-II luminescence is revealed in MgO:Cr3+,Ni2+ phosphor.•Performance: QY = 92.7 %, FWHM = 235 nm, thermostable (83.0 %@150 ℃).•The efficient NIR-II pc-LED device (27.4 mW at 350 mA) is fabricated.•The application potential of this NIR-II light source is demonstrated. The development of phosphor-converted light-emitting diodes (pc-LEDs) in the second near-infrared window (NIR-II, 1000–1700 nm) represents an important, newly emerging, and dynamic field in NIR spectroscopy. Unfortunately, lacking efficient NIR-II phosphors that can be excited by commercial blue LED chips impedes NIR spectroscopy applications. Herein, a donor–acceptor strategy is developed by introducing Cr3+ sensitizers to greatly enhance the blue-light excitation efficiency of NIR-II-emitting MgO:Cr3+,Ni2+ phosphor. Consequently, a high-efficiency blue-light-excitable MgO:Cr3+,Ni2+ phosphor that gives a NIR-II emission at 1335 nm with a full width at half-maximum (FWHM) of 235 nm, is demonstrated. The product has a high internal quantum efficiency of 92.7 % and excellent thermal stability, maintaining 83.0 % of the room temperature emission intensity at 150 °C. Excitingly, the fabricated NIR-II pc-LED device shows a high NIR-II optical power (27.4 mW@350 mA). The performances of the achieved NIR-II pc-LED are almost the best results until now. Additionally, multifunctional applications including nondestructive detection and anti-counterfeiting of the NIR-II light source are demonstrated. These results are pretty crucial for the further development of NIR-II spectroscopy and imaging technology.