The chemical structure of pyrazole-1-carbothioamide derivative 1 was modified through building a thiazole moiety to synthesize derivatives of thiazolyl pyrazolin-5-one. The reaction of 1 with phenacyl bromide furnished the conforming thiazolyl pyrazole derivative 2, which upon base-catalyzed reaction with benzyl isothiocyanate afforded thiazolyl 4-(benzylthiocarbamoyl)-2-pyrazolin-5-one derivative 3. The diazo-coupling reaction of 2 with diazotized 4-aminoacetophenone afforded the conforming thiazolyl 4-(p-acetylphenylhydrazono)-2-pyrazolin-5-one derivative 4. The synthesized thiazolyl pyrazolin-5-one derivatives were utilized as antioxidant additives for lubricating oil. The oxidation stability study revealed that the tested compounds showed good antioxidant activities. The efficiency of the tested antioxidant additives decreases according to the order: compound 2 > compound 4 > compound 3 > compound 1.