The present invention relates to a negative electrode active material for secondary batteries, and a negative electrode, an electrode assembly and a secondary battery including the same. The negative electrode active material includes polyhedral crystalline carbon, a first surface treatment layer disposed on a surface of the crystalline carbon and including amorphous carbon or oxidized crystalline carbon, and a second surface treatment layer disposed on a surface of the first surface treatment layer and including a polyacrylic acid ester copolymer, thereby improving output characteristics of batteries based on increased mobility of electrons resulting from surface-to-surface contact between active materials, controlling reactivity with an electrolyte, and enhancing high-temperature storage performance of batteries.