Nonsteroidal anti-inflammatory drugs (NSAIDs) cause peptic lesions in the gastrointestinal mucosa by inhibiting the cyclooxygenase-1 (COX-1) enzyme. Selective COX-2 inhibition causes decreased side effects over current NSAIDs. Therefore, the studies about selective inhibition of COX-2 enzyme are very important for new drug development. The design, synthesis and biological activity evaluation of novel derivatives bearing thiazolylhydrazine-methyl sulfonyl moiety as selective COX-2 inhibitors were aimed in this paper. The structures of synthesized compounds were assigned using different spectroscopic techniques such as H-1 NMR, C-13 NMR and HRMS. In addition, the estimation of ADME parameters for all compounds was carried out using in silico process. The evaluation of in vitro COX-1/COX-2 enzyme inhibition was applied according to the fluorometric method. According to the enzyme inhibition results, synthesized compounds showed the selectivity against COX-2 enzyme inhibition as expected. Compounds 3a, 3e, 3f, 3g, 3i and 3j demonstrated significant COX-2 inhibition potencies. Among them, compound 3a was found to be the most effective derivative with an IC50 value of 0.140 +/- 0.006 mM. Moreover, it was seen that compound 3a displayed a more potent inhibition profile at least 12-fold than nimesulide (IC50 = 1.684 +/- 0.079 mu M), while it showed inhibitory activity at a similar rate of celecoxib (IC50 = 0.132 +/- 0.005 mu M). Molecular modelling studies aided in the understanding of the interaction modes between this compound and COX-2 enzyme. It was found that compound 3a had a significant binding property. In addition, the selectivity of obtained derivatives on COX-2 enzyme could be explained and discussed by molecular docking studies. (C) 2020 Elsevier Masson SAS. All rights reserved.