A previous study demonstrated that a β-N-acetyl-D-hexosaminidase (NlHex4) from the brown planthopper could serve as a new potential target for biopesticides due to its requirement for molting, and lethal phenotypes were observed via RNA interference. However, the enzymatic properties of NlHex4 remain unclear. In the present study, NlHex4 was expressed, purified and characterized. Recombinant NlHex4 was functionally expressed in baculovirus-infected insect cells and purified with a molecular weight of approximately 70 kDa. Recombinant NlHex4 had an optimal pH and temperature of 6.0 and 60 °C, respectively. Moreover, recombinant NlHex4 exhibited thermal stability at 50 °C for at least 1 h. Furthermore, the activity of recombinant NlHex4 was inhibited by the metal ions Fe2+ and Fe3+ and the serine protease inhibitor phenylmethanesulfonyl fluoride. These results reveal the enzymatic properties of NlHex4 and provide a basis for future investigation of the interaction between HEX and chitin oligosaccharide.