Beta-glucosidases play an important role in the hydrolysis of cellulose and are among the cellulases in termites responsible for cellulose degradation and regulation of gene expression. A cDNA encoding putative β-glucosidase (CfBGIa) from the Formosan subterranean termite, Coptotermes formosanus Shiraki, was successfully cloned. The full-length of the cDNA of CfBGIa was 2,195 base pairs (bp) with an open reading frame of 1,500 bp that encoded for a 499–amino acid protein. Excluding a putative signal peptide of the first 21 amino acid residues, the 478-residue mature CfBGIa has a calculated molecular mass of 54.49 kDa. Sequence assessment and phylogenetic analysis suggested that CfBGIa belongs to β-glucosidase cluster I (BG-I group) encoding digestive enzymes. Homology modeling shows a classical (β/α)₈ barrel structure of glycosyl hydrolase family 1 including two catalytic residues, Glu193 and Glu402. Quantitative PCR analysis in different temperatures revealed a similar expression pattern between CfBGIa and Co. formosanus clone Glu1B β-glucosidase mRNA. Both genes were induced in low (4°C) and high (38°C) temperatures. CfBGIa may prove to be a supplement to the cellulase system to improve the cellulose digestion in the termite, and these results might contribute to mining novel cellulases for cellulosic conversion.