Indonesian Mistletoe, Dendrophthoe pentandra (L.) Miq., has been reported as a medicinal plant containing interesting pharmacologically bioactive compounds. However, the bioactive compounds of each part of the plant can be different. Thus, we investigated the chemical contents of two organs of D. pentandra (leaves and flowers) by various chemical reagent tests and compared the antioxidant activity of the two organs. Both leaves and flowers samples were extracted with methanol to yield crude extracts. The results showed that both extracts contained alkaloids, tannins, flavonoids, saponins, and terpenoids. Quantitative test showed that the flowers extract contained more phenols and flavonoids compared to the leaves extract. DPPH assay also confirmed that flowers extract presented higher IC50 compared to leaves extract. These results suggested that phenols and flavonoids may function as antioxidant agents in D. pentandra. However, further study is needed to investigate whether there are differences of phenols and flavonoids types in leaves and flowers of D. pentandra.