Excited-state intramolecular proton transfer (ESIPT) was studied for two different fluorophores M2N3HF and 2P3HBQ in binary solvent mixtures of n-heptane and methanol. While both fluorophores share a degree of structural resemblance, they exhibit sharply contrasting ESIPT dynamics in the solvent mixtures. For 2P3HBQ, ESIPT is ultra-fast in n-heptane, followed by monotonic retardation in the solvent mixtures as the proportion of methanol increases, due to the predominance of 2P3HBQ⋯Methanol intermolecular H-bonding over intramolecular H-bonding within the 2P3HBQ molecule, at high methanol concentrations. For M2N3HF on the other hand, ESIPT is known to occur within sub-picosecond time-scales in alkanes and within few tens of picoseconds in methanol. However, addition of minor quantities of methanol into an alkane solvent like n-heptane causes the ESIPT to be dramatically arrested: even at 3 % mole fraction of methanol, it requires several 100 ps to complete, thus becoming ∼ 1000-fold slower than that in pure n-heptane, and ∼ 5-fold slower than that in pure methanol. Our results demonstrate that the ESIPT time-constants of M2N3HF in the solvent mixtures follow the same trend as solvation time-constants, suggesting that solvent relaxation plays a major role in the re-distribution of intra- and intermolecular H-bonds in the excited state M2N3HF. Unlike 2P3HBQ, the ESIPT of M2N3HF is thus coupled to the solvation dynamics of the solvent medium.