Chitinases are the enzymes that cleave chitin. Even in the absence of chitin, mammalians have significant amounts of chitinases present in the body including at baseline. The precise role of chitinase is not known, however it was believed to play important role in digestion and host defense against chitin-containing food and pathogens, respectively. Recent work, including ours, has shown an important role of chitinase and chitinase-like proteins in host immunity and allergic diseases. Importantly, chitinase activities serve as important biomarkers of disease severity in a wide-range of diseases including type 2 inflammatory diseases such as asthma and pulmonary fibrosis. Similarly, patients with genetic disorders like Gaucher disease have significantly elevated chitinase levels, which not only correlate with disease severity but also serve as a reliable biomarker for therapeutic effectiveness. The protocol outlined here describes a simple, quick, and straightforward way to measure chitinase activity in BAL or serum samples of mice and can be widely adapted to human subjects and other model organisms due to the highly conserved nature of the enzymes.