Biochemical characterization of the recombinant gene products from the Arabidopsis glucosyltransferase multigene family has identified one enzyme with high activity toward the plant cellular regulator jasmonic acid (JA). The protein, AtJGT1 (UDP-glucose:JA glucosyltransferase), also has significant activities with other substrates, such as dihydrojasmonic acid, indole-3-acetic acid (IAA), indole-3-propionic acid, and indole-3-butyric acid. The $K_m$ values of AtJGT1 for JA or IAA are similar to those of an Arabidopsis IAA glucosyltransferase UGT84B1 previously reported. Northern blot analysis showed that At/Gr1 is highly expressed in the leaves, but only slightly detectable in the roots, stems, and inflorescences. This study describes the first biochemical analysis of a recombinant glucosyltransferase with JA activity, and provides the foundation for future genetic approaches to understanding the role of JA-glucose in Arabidopsis.