In the present work, new indole-based chalcone derivatives were obtained via the reaction of 5-substituted-1H-indole-3-carboxaldehydes/1-methylindole-3-carboxaldehyde with appropriate acetophenones. The synthesized compounds were investigated for their in vitro COX-1 and COX-2 inhibitory activity. The most effective COX inhibitors were also evaluated for their in vivo antiinflammatory and antioxidant activities in LPS induced sepsis model. Furthermore, the CCK-8 assay was carried out to determine cytotoxic effects of all compounds against NIH/3T3 mouse embryonic fibroblast cells. 3-(5-Bromo-1H-indol-3-yl)-1-(4-cyanophenyl)prop-2-en-1-one (6) can be considered as a non-selective COX inhibitor (COX-1 IC₅₀ = 8.1 ± 0.2 μg/mL, COX-2 IC₅₀ = 9.5 ± 0.8 μg/mL), whereas 3-(5-methoxy-1H-indol-3-yl)-1-(4-(methylsulfonyl)phenyl)prop-2-en-1-one (1) inhibited only COX-1 (IC₅₀ = 8.6 ± 0.1 μg/mL). According to in vivo studies, these compounds also displayed antiinflammatory and antioxidant activities.