Rhododendron species (Ericaceae) is considered the most diverse group, with more than 1200 species famous for their colorful flowers. Rhododendron, also known as azalea, is a flowering tree in the Ericaceae family. Herein, in vitro antioxidant activities of acetone and methanol extracts of Rhododendron ponticum leaves were studied along with their phenolic contents using High-Performance Liquid Chromatography with a Diode-Array Detector (HPLC-DAD). Antioxidant activity was performed spectrophotometrically using ABTS·+, DPPH·, CUPRAC, and β-carotene/linoleic acid assays. Acetone extract showed better antioxidant activity than methanol extract in all tests. The HPLC-DAD analysis revealed fifteen phenolic compounds, of which seven were common for both extracts. Catechin (25.80 and 33.08 mg/g extract, respectively) and epicatechin (31.15 and 26.54 mg/g extract, respectively) were calculated as major phenolic components in acetone and methanol extracts.