A new class of 4-arylhydrazono-1-benzothiazolyl-3-methylpyrazolin-5-ones (3a–j) and 4-arylazo-1 benzothiazolyl-3,5-dimethylpyrazoles (4a–j) were designed as pharmacophore hybrids between pyrazolinone/pyrazole and benzothiazole moiety. The target molecules were efficiently synthesized by the cyclization of various oxobutyrates/pentane-2,4-dione derivatives with 6-chloro-2 hydrazinobenzothiazole in the presence of glacial acetic acid. The compounds were evaluated for their in vitro antimicrobial activity. Preliminary study of the structure– activity relationship revealed that electron-withdrawing groups in phenyl ring had a promising effect on the antimicrobial activity. Also, correlation study has been used to establish the relationships between the antibacterial activity and physicochemical parameter clogP.