Mushrooms have been used for both culinary and medicinal reasons for a very long time. Mushrooms are useful as both a food and a medication due to their high nutritional, protein, vitamin, and phenolic content. The current research aims to determine the antioxidant activity and phenolic content of Hebeloma sinapizans. Multiple epidemiological research looked at the possible link between polyphenol consumption and cardiovascular illness. Antioxidant, antiplatelet, antiinflammatory, antilipidemic, and antihypertensive are the categories used to classify the actions of phenolic substances. HPLC was used to isolate the phenolic compounds (HPLC). Measurements of oxidative stress, total oxidant levels, and total antioxidant levels were all calculated with the use of Rel Assay kits. The mushroom's TAS, TOS, and OSI values were measured, and its gallic acid, chlorogenic acid, and cinnamic acid concentrations were identified. Due to its high levels of phenolic compounds, H. synapizans is thought to be a source of phenolic compounds. High TAS and TOS values and low OSI values indicate that the mushroom has antioxidant potential. As a result, it has been seen that H. synapizans can be a good source of antioxidants.