Acacia honey is a popular and high-value monofloral honey. On the honey market, immature acacia honey is sometimes thermally dehydrated, yielding a fraudulent product - artificially heated acacia honey (AHAH). Typical physicochemical indices are not sufficient to distinguish AHAH from naturally matured acacia honey (NMAH). Using a UHPLC-Q-TOF-MS-based metabolomics approach, we compared the aqueous solutions of 33 NMAH and 33 AHAH samples, and uncovered a differential compound with a mass of 327.1321 Da. Structural analysis, employing high resolution-mass spectrometry (HR-MS) combined with nuclear magnetic resonance (NMR), identified it as N-(1-deoxy-1-fructosyl) phenylalanine (Fru-Phe), an Amadori compound that forms in the initial stages of the Maillard reaction and can be as a sensitive index for thermal treatment. According to quantitation via UHPLC-MS/MS, Fru-Phe was < 1.54 mg/kg in NMAH and > 10.00 mg/kg in AHAH, showing Fru-Phe is a potential indicator of artificial heating acacia honey.