The title compound, C8H4BrNO2·0.5H2O, has a single planar molecule in the asymmetric unit with the non-H atoms having a mean deviation from planarity of 0.028 Å. There is also a half of a water molecule (twofold symmetry) present in the asymmetric unit, which hydrogen bonds with the isatin molecules through O—H...O and N—H...O hydrogen bonds to form a two-dimensional framework in the ab plane. There are close Br...O contacts of 2.999 (2) Å to link the layers. The nine-membered rings of the isatin molecules stack along the a axis with parallel slipped π–π interactions [inter-centroid distances = 3.6989 (19) and 4.1227 (19) Å].
