We report on the solvent influence on the two-photon absorption spectra of p-nitroaniline. Measurements of the two-photon absorption cross section values were performed in three solvents (1,4-dioxane, propylene carbonate, dimethyl sulfoxide) using the Z-scan technique. The most important finding in this report is the observation that two-photon absorption cross section value, corresponding to the intramolecular charge-transfer state, is significantly intensified with the solvent polarity increase. In the case of a strongly positive solvatochromic molecule, the two-level model correctly predicts the observed two-photon absorption cross section value increase caused by the solvent polarity change.