High temperatures can harm plants and reduce crop yield. Gibberellic acid (GA3) is a plant hormone that helps plants grow and cope with stress. In this experiment, mung bean seedlings were exposed to heat stress with and without GA3. The lethal temperature was found to be 50°C for 2 hours, which decreased amylase activity in all genotypes. However, pre-treating with a milder temperature (40°C for 1 hour) before the lethal temperature increased amylase activity. GA3 application helped increase amylase activity under heat stress. Different mung bean genotypes showed varying levels of amylase activity and heat stress tolerance, with NM 19-19 being the most tolerant and NM 20-21 being the least.