High-entropy alloy (HEA) represents innovative frontier in catalysis, which offers many advantages originated from its multiple metals and structural attributes. Herein, a PtRhCoNiMn nanodendritic HEA (NDHEA) was synthesized by a simplified one-pot oil-phased co-reduction method, as evidenced by a set of characterization techniques. The resulting catalyst significantly reduced the reliance on costly Pt while achieving exceptional catalytic performance, as certificated by hydrogenation of 4-nitrophenol (4-NP) and Cr (VI) as proof-of-concept models, showing normalized rate constant (k