A gene encoding heat shock transcription factor (HSF) was cloned and sequenced from cultured cells of the cabbage armyworm, Mamestra brassicae. The cDNA potentially encoded a 699‐aa protein, with a calculated molecular weight of 77.8 kDa. Deduced amino acid identities to HSFs from Aedes aegypti and Drosophila melanogaster were 36 and 34%, respectively. Analysis of the genomic DNA revealed eight exons and three optional exons: a, b, and c. Exon a contained a premature in‐frame stop codon that would generate a truncated protein. When the cells were exposed to high temperature or cadmium, no particular alternative transcripts showed significant up‐ or down‐regulated expression relative to the total amount of the transcripts. These results suggest that alternative splicing may not be a principal mechanism for regulation of M. brassicae HSF gene expression in response to heat shock and cadmium. © 2009 Wiley Periodicals, Inc.