Costus speciosus (J.Koenig) Sm., also known as ‘Insulin plant’, is an erect rhizomatous herb belonging to the Costaceae family. It holds significant potential for the development of pharmaceutical drugs due to the abundance of bioactive secondary metabolites. In this study, we screened the ethanolic extract of C. speciosus rhizome (CSE) for its phytochemical composition, anti-inflammatory potential, and non-toxic behaviour towards gut bacteria Lactobacillus casei. The CSE displayed the presence of a variety of phytochemicals such as saponins, coumarins, tannins, terpenoids, alkaloids, phenolics, etc. It contained significant total saponin (4.68 ± 0.12 gm/100 gm of oleanolic acid equivalents), terpenoid (192.54 ± 4.18 mg linalool/gm of dry weight), and phenolic (64.59 ± 1.96 mg GAE/gm) content. The in-vitro anti-inflammatory activity of CSE expressed as percentage inhibition was found to be 76.2 ± 2.20 % at 1000 μg/ml. Additionally, the CSE (50, 100, and, 250 µg/disc) did not harm the growth of Lactobacillus casei. The presence of several phytochemicals, their significant content, and remarkable in-vitro anti-inflammatory activity, all point to the exceptional medicinal potential of C. speciosus.