THE VERSATILE synthon 2-Amino-4-(thiophene-2-yl) thiophene-3-carbonitrile (1) was used as precursor for the synthesis of a series of bithiophene (2) and thieno [2, 3-d] pyrimidine (3) derivatives. The antimicrobial evaluations of the newly synthesized compounds were carried out in vitro assays for antifungal and antibacterial activities. Amongst the tested compounds, 1-(4\-cyano-2,3\-bithiophen-5\-yl)3-phenylthiourea (2b), 4-imino-3-phenyl-5-(thiophenyl-2-yl)-3,4-dihydrothieno[2,3-d] pyrimidine-2(1H)-thione (3b) and 1-phenyl-3-(5-(thiophenyl-2-yl)thieno[2,3-d]pyrimidin-4-yl) thiourea (5c) exhibit significant antibacterial activities against Pseudomonas sp, Escherichia coli, Streptococcus lactis, Bacillus subtilis and exhibit significant antifungal activities against Aspergillus niger, Penicillium sp, Candida albicans and Rhodotorula ingeniosa. From structure-activity relationship (SAR) point of view, the attachment of phenyl thioureido moiety to bithiophenes can be considered as a breakthrough in developing a new therapeutic antimicrobial agents related to bithiophene system.