The results of the quantum-chemical investigation of a series of hydrogen-bonded 1:1 acid–base complexes formed by model phosphinic acids, Me₂POOH, and PhHPOOH, are reported. A series of substituted pyridines (pK_a range from 0.5 to 10) was chosen as proton acceptors. Gradual changes of isotropic ³¹P nuclear magnetic resonance (NMR) chemical shift, δP, were correlated with the bridging proton position in the intermolecular OHN hydrogen bond, namely, r (OH) distance; the proposed correlation could easily be extended to other phosphinic acids as well. For complexes with pyridine and 2,4,6-trimethylpyridine, we have investigated in more detail several factors influencing the δP values: (1) the proton transfer within the OHN hydrogen bond; (2) the rotation of the pyridine ring around the hydrogen bond axis (associated with the formation/breakage of additional weak P-O···H–C hydrogen bond); and (3) the rotation of the phenyl substituent in phenylphosphinic acid around the P–C axis. All these factors appeared to be of similar magnitude, thus masking their individual contributions that have to be independently estimated for a reliable spectral interpretation.