Calotropis procera it is known for traditional Kenyan medicinal system and it is used for it has previously been employed for treatment various diseases. This study aimed at examining methanolic extract of C. procera to establish antioxidant potential in vitro, total phenolic and flavonoid contents in order to identify potential sources of new antioxidants in food and pharmaceutical formulations. A comprehensive assessment on the antioxidant activity of stem back and root of C. procera by in vitro chemical analyses. Total phenolic, total flavonoid contents and total yield of the samples were also estimated. Preliminary phytochemical tests were also carried out to establish the components of plant extracts. Results of the study revealed presence of saponins terpenoids, alkaloids, anthraquinones and steroids. The stem back extract had significantly higher amounts of total phenol and flavonoid contents (79.80±3.79 mg GAE/g extract and 71.63±4. mg RTE/g extract, respectively) compared to root samples. We established correlation between total phenolic contents and EC50 values for DPPH free radical scavenging property and reducing power of extract, ABTS radical cation and phosphomolybdate. Taken together, this work demonstrated considerable protective effectiveness in C. procera stem back and root methanolic extracts that function as an antioxidizing agent due to their free radical scavenging activity.