Abstract: Although azurite is one of the most important copper oxide minerals, the recovery of this mineral via sulfidization–xanthate flotation is typically unsatisfactory. The present work demonstrated the enhanced sulfidization of azurite surfaces using ammonia phosphate ((NH₄)₃PO₄) together with Na₂S, based on micro-flotation experiments, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), zeta-potential measurements, contact angle measurements, Fourier-transform infrared (FT-IR) spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. Micro-flotation experiments showed that the floatability of azurite was increased following the simultaneous addition of (NH₄)₃PO₄ and Na₂S. ToF-SIMS and XPS analyses demonstrated the formation of a high content of S species on the azurite surface and an increase in the number of Cu(I) species after exposure to (NH₄)₃PO₄ and Na₂S, compared with the azurite–Na₂S system. The zeta potential of azurite particles was negatively shifted and the contact angle on the azurite surface was increased with the addition of (NH₄)₃PO₄ prior to Na₂S. These results indicate that treatment with (NH₄)₃PO₄ enhances the sulfidization of azurite surfaces, which in turn promotes xanthate attachment. FT-IR and UV–Vis analyses confirmed that the addition of (NH₄)₃PO₄ increased the adsorption of xanthate with reducing the consumption of xanthate during the azurite flotation process. Thus, (NH₄)₃PO₄ has a beneficial effect on the sulfidization flotation of azurite.