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Nowadays, red phosphor plays a key role in improving the lighting quality and color rendering index of phosphor‐converted white light emitting diodes (w‐LEDs). However, the development of thermally stable and highly efficient red phosphor is still a pivotal challenge. Herein, a new strategy to design antithermal‐quenching red emission in Eu3+, Mn4+‐codoped phosphors is proposed. The photoluminescence intensity of Mg3Y2(1− y )Ge3O12:yEu3+, Mn4+ (0 ≤ y ≤ 1) phosphors continuously enhances with rising temperature from 298 to 523 K based on Eu3+ → Mn4+ energy transfer. For Mg3Eu2Ge3O12:Mn4+ sample, the integrated intensity at 523 K remarkably reaches 120% of that at 298 K. Interestingly, through codoping Eu3+ and Mn4+ in Mg3Y2Ge3O12, the photoluminescence color is controllably tuned from orangish‐red (610 nm) to deep‐red (660 nm) light by changing Eu3+ concentration. The fabricated w‐LEDs exhibit superior warm white light with low corrected color temperature (CCT = 4848 K) and high color rendering index (R a = 96.2), indicating the promising red component for w‐LED applications. Based on the abnormal increase in antistokes peaks of Mn4+ with temperatures, Mg3Eu2Ge3O12:Mn4+ phosphor also presents a potential application in optical thermometry sensors. This work initiates a new insight to construct thermally stable and spectra‐tunable red phosphors for various optical applications., A proposal for designing antithermal‐quenching red phosphors with consecutive emission enhancement (beyond 120%) up to 523 K and controllably luminescence color adjustment from orange to deep red light based on Eu3+ → Mn4+ energy transfer for potential application in white light emitting diodes and optical low‐temperature thermometry sensors is presented.