The equilibrium solubility of 3- and 4-nitrophthalic acids in water was measured experimentally using Schreinemaker's wet residue method at temperatures ranging from (285.15 to 348.15) K at atmospheric pressure. The solubility of 3- and 4-nitrophthalic acids in water increased with the increase of temperature. The experimental solubility is correlated by an empirical equation. The calculated values via the empirical equation agreed well with experimental results for 3- and 4-nitrophthalic acids.