In this work, an organic-inorganic hybrid crystal with excellent bactericidal activity, 4-methyl-1-(2'-nitrobenzyl)pyridinium tetrabromocuprate(II) ([4Me2NO2BzPy]2[CuBr4]), was synthesized by the crystal growth by a slow evaporation method and characterized. [4Me2NO2BzPy]2[CuBr4] crystallized in the orthorhombic space group Pna21. Hirshfeld surface analysis indicated that the H···H (28.8%), H···Br/Br···H (27.0%), and O···H/H···O (17.5%) interatomic contacts played a primary role in contributing to the stacking of the crystals. Thermogravimetric analysis showed that the material was stable up to 192.5 °C. The charge transfer interaction between anions and cations was explained by UV-Vis diffuse reflectance spectroscopy. [4Me2NO2BzPy]2[CuBr4] exhibited favorable bactericidal activity against Staphylococcus aureus and Escherichia coli.