The current study aimed to assess broccoli's phytochemical profile and determine its antioxidant activity. Fresh broccoli was procured from a local farm and divided into two major treatment groups (cooked and dried). There were five sub-treatments in the cooking group (conventional, microwave, boiling, blanching, and steaming) and three treatments in the drying group (sun drying, freeze drying, and hot air drying). Ascorbic acid content, total carotenoids, TPC, TFC, and antioxidant activity were evaluated for every sub-treatment. The results depicted that the antioxidant constituent of cooked broccoli was complementary to dried broccoli samples. The maximum amount of ascorbic acid content (10.80 mg/100 g), total carotenoids (3.976 mg/g), total phenolic contents (225.80 mg/g), and the total flavonoid contents (42.92 mg/g) were found in freeze-dried broccoli. Freeze-dried broccoli also showed the highest antioxidant activity for DPPH free radical scavenging assay (62.45%), hydrogen peroxide radical scavenging assay (53.67%), and ABTS radical scavenging assay (65.84%).