The design, synthesis and pharmacological activities of a group of 5,5-diphenylimidazolidine-2,4-dione bearing anilide, phenacyl and benzylidene fragments 2-27 were reported. The prepared 5,5-diphenylimidazolidine-2,4-dione derivatives were evaluated in vivo for anti-inflammatory, analgesic activities and in vitro for COX-1/2 inhibition assay. Among the tested compounds, derivatives 5, 9, 10, 13, and 14 showed significant and potent anti-inflammatory and analgesic activities almost equivalent to reference drug celecoxib. In COX-1/2 inhibition assay, compounds 5, 9, 10 and 14 showed high COX-2 inhibitory activity (IC50 = 0.70 μM, 0.44 μM, 0.61 μM and 0.41 μM; respectively) and selectivity index (SI) range of 142-243 comparable to celecoxib [COX-2 (SI) > 333]. These potent COX-2 inhibitors 9, 10, 13, and 14 were docked into the active site pocket of COX-2 to explore the binding mode and possible interactions of these ligands.