The Gamma-Ray Imaging Detector (GRID) on board AGILE detected the long bright GRB 100724B (Bhat, GCN 10977; Tanaka et al., GCN 10978; Golenetskii et al., GCN 10981; Marisaldi et al., GCN 10994) in the energy range 25 – 500 MeV with a statistical significance larger than 9 sigma. The gamma-ray emission observed by the AGILE-GRID instrument lasted about 100 seconds, and two peaks are evident in the lightcurve consistent with the behaviour reported by Fermi LAT. See AGILE GCN number 10996.