The crystal structures, synthesis procedure, thermal behavior, and spectroscopic properties of a new squaraine SqINH center dot H2O and its anhydrous arrangement are described. This squaraine is obtained through an acid-base reaction using squaric acid (H(2)Sq) and isoniazid (INH) as precursors. Both squaraines crystallize in the monoclinic system, but in different space groups: the hydrated and anhydrous arrangement crystallizes in the P2(1) and P2(1)/c space group, respectively. The crystallographic data strongly suggest that the structures present an expressive increase in their electronic delocalization all over the molecular structure of both compounds, when compared with the reagents. The bond distances for both structures present an average value intermediate between a single and double character (1.463(3) angstrom for SqINH center dot H2O and 1.4959(3) angstrom for SqINH). The vibrational and electronic data also corroborate with this proposal, since the band shifts indicate that the conjugation over the system is increased, as indicated by the blue shift observed for the carbonyl stretching bands for both compounds. The presence of the water molecule is responsible for a decrease in fluorescence emission, as determined by the emission spectra recorded for both compounds.