Transgenic lines of oil seed plant Brassica juncea expressing a synthetic cry1Ac gene were developed using Agrobacterium tumefaciens-mediated transformation. The integration of transgene cry1Ac in transformed plants was confirmed by Southern blot hybridization using a cry1Ac probe. Expression of transgene was analyzed using reverse transcription PCR. Inheritance of the hpt gene in transgenic plants showed the expected 3:1 Mendelian segregation ratio. An enzyme linked immuno sorbent assay revealed that Cry1Ac protein content in the leaves of transgenic plants (T₀, T₁ and T₂) ranged from 250 to 1,800 ng mg^-1 of total soluble protein. The insect bioassay study showed that transgenic plants were resistant to 2nd instar larvae of Plutella xylostella as compared to control plants and confirmed the enhanced insect resistance in Indian mustard.