Considerable efforts have been devoted to the development of visible light-emitting phosphors for anti-counterfeiting application, but the design of multifunctional near-infrared materials with suitable luminescent properties was lacking. Based on the crystal field theory, a near ultraviolet excitable and near-infrared emitting Ca2Sn2(1-x)Al2(1-x)O9:2xCr3+,2xSi4+ phosphor was designed. On the one hand, the Ca2Sn2(1-x)Al2(1-x)O9:2xCr3+,2xSi4+ phosphor showed great potential for applications including anti-counterfeiting and secret signals under a 405 nm near UV laser. The integrated intensity at 150 °C was 75.9%, implying high thermal stability when irradiated with a high power light source. On the other hand, an unexpected red emission component originating from the Cr3+-Cr3+ dimer was observed and was confirmed by fast luminescence decay and electron spin resonance signals. The different thermal stabilities of Cr3+ near-infrared and Cr3+-Cr3+ red emissions opened up a new opportunity for luminescence ratiometric thermometers.