The addition of either sodium hydroxide or tetramethylammonium hydroxide to 3-nitrophenol led to orange-red crystals of sodium 3-nitrophenolate dihydrate or a complex of 3-nitrophenol and tetramethylammonium 3-nitrophenolate. For the sodium salt, 11707 Mo-Kα reflections were measured at 150 K via Bruker SMART 1-K CCD diffractometer. For the tetramethylammonium salt, 12664 Mo-Kα reflections were measured at 173 K via Bruker SMART 2-K CCD diffractometer. The unit cell of the sodium salt has: a = 6.814(1) Å, b = 6.5437(8) Å, c = 18.206(4) Å, β = 94.46(3)°, V = 809.4(3) Å3, space group = P21/n. The unit cell of the tetramethylammonium salt has: a = 23.543(4) Å, b = 5.636(1) Å, c = 16.387(3) Å, β = 128.513(3)°, V = 1701.4(9) Å3, space group = C2/c. The bond lengths of the 3-nitrophenolate moiety were statistically the same in the two crystal structures, showing that it is not affected by the cation