Background:This study investigates the analgesic properties of the aqueous extracts of Nigella sativa and Eucheuma cottonii in mice. The analgesic properties of both extracts were evaluated in an experimental model of acetic acid-induced writhing test.Materials and Methods:The mice were divided into four different groups and received the test extracts and the standard drug (aspirin) for 14 days via force-feeding. On day 15, the mice were injected with 5% acetic acid, and the number of abdominal constriction and elongation of hind limb (writhes) were counted for 20 min.Results:The numbers of writhes were counted starting after 5 min of the acetic acid injection. The N. sativa extracts significantly reduced the number of writhes as compared to the control group. Both of the extracts revealed a comparable result as referred to the aspirin effects in the mice.Conclusions:These findings indicate that N. sativa and E. cottonii may possess protective active constituent that is effective in reducing the sensation of pain in mice.