A series of substituted ethylidenehydrazinylidene-1,3-thiazol-4-ones and dimethyl 2-[4-1(-[5-(2-methoxy-2-oxoethylidene)-4-oxo-3-phenyl-1,3-(thiazolidin-2-ylidene]hydrazonylidene}ethyl)phenyl]aminofumarate were synthesised by condensation of substituted ethylidene- N-phenylhydrazinecarbothioamides with dimethyl acetylenedicarboxylate. The synthesised compounds were characterised by spectroscopic methods and confirmed by single crystal X-ray crystallography. Some of the prepared compounds were screened for their in vitro antibacterial activity against different strains of microorganisms, compound 3b exhibited significant antibacterial activity against Pseudomonas aeruginosa compared to ciprofloxacin with MIC value of 1.12 μg mL−1.