Several 1-(4-aryl-2-thiazolyl)-3-(2-thienyl)-5-aryl-2-pyrazoline derivatives were synthesized by reacting substituted 3-(2-thienyl)-5-aryl-1-thiocarbamoyl-2-pyrazolines with phenacyl bromides in ethanol. The structures of the synthesized compounds were confirmed by (1)H NMR, (13)C NMR, and EIMS spectral data. Their antimicrobial activities against Escherichia coli (NRRL B-3704), Staphylococcus aureus (NRLL B-767), Salmonella typhimurium (NRRL B-4420), Bacillus cereus (NRRL B-3711), Streptococcus faecalis (NRRL B-14617), Aeromonas hydrophila (Ankara Uni. Fac. of Veterinary), Candida albicans and Candida glabrata (isolates obtained from Osmangazi Uni. Fac. of Medicine) were investigated. A significant level of activity was observed.