A strategy for the direct functionalization strategy of inertial dialkyl phosphonates with hydroxy compounds to afford diverse mixed phosphonates with good yields and functional‐group tolerance has been developed. Mechanistic investigations involving both NMR studies and DFT studies suggest that an unprecedented highly reactive PV species (phosphoryl pyridin‐1‐ium salt), a key intermediate for this new synthetic transformation, is generated in situ from dialkyl phosphonate in the presence of Tf2O/pyridine. Mild thing, you make my heart sing: The application of Tf2O to phosphorus chemistry was expanded to the generation of electrophilic P‐species. A metal‐free activation of stable dialkyl phosphonates was developed that enables the synthesis of diverse mixed phosphonates. The reaction proceeds under mild conditions and exhibits a broad substrate scope and excellent functional‐group tolerance. NMR studies and DFT calculations provide insight into the mechanism.