A novel bismuth(III) complex with 2-amino-3-carbomethoxy-4,5,6,7-tetrahydrobenzo[b]thiophene (ACTT) as a ligand have been synthesized. The novel complex was characterized on the basis of its IR, NMR, elemental analysis and MS spectral data. It was found that the ligand behaves as a monodentate chelating agent and bonds to the metal ion through the nitrogen atom of the amino group to form the [BiIII(ACTT)6]Cl3 complex. The new complex compound displayed significant antimicrobial activity (MIC = 8-32 µg/mL) against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Shigella flexneri, Candida albicans, Candida tropicalis and Cryptococcus neoformans.