All open systems that exchange energy with their environment are non‐Hermitian. Thermal emitters are open systems that can benefit from the rich set of physical phenomena enabled by their non‐Hermitian description. Using phase, symmetry, chirality, and topology, thermal radiation from hot surfaces can be unconventionally engineered to generate light with new states. Such thermal emitters are necessary for a wide variety of applications in sensing and energy conversion. Here, a non‐Hermitian selective thermal emitter is experimentally demonstrated, which exhibits passive PT‐symmetry in thermal emission at 700 °C. Furthermore, the effect of internal phase of the oscillator system on far‐field thermal radiation is experimentally demonstrated. The ability to tune the oscillator phase provides new pathways for both engineering and controlling selective thermal emitters for applications in sensing and energy conversion.