Bacterial pathogens of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) were investigated. Two different pathogenic bacteria were isolated from unhealthy and dead larvae. They were identified as Pantoea agglomerans (Ewing and Fife) and Alcaligenes piechaudii Kiredjian et al. on the basis of fatty acid methyl ester (FAMEs) analysis and carbon utilization profiles by using Microbial Identification and Biolog Microplate Systems. Laboratory experiments carried out to determine insecticidal activities of these isolates showed that Pantoea agglomerans and Alcaligenes piechaudii have 95.0% and 98.75% mortality on third-instar larvae of H. armigera, respectively, after 14 days. This is the first study to demonstrate that Pantoea agglomerans and Alcaligenes piechaudii are pathogenic bacterial flora of H. armigera. These bacteria may have great potential for use in biological control of H. armigera.