An anode active material for a lithium secondary battery and a lithium secondary battery having the same are disclosed. The anode active material for a lithium secondary battery includes a silicon alloy consisting of silicon and at least two kinds of metals other than silicon, each having the heat of mixing with the silicon of −23 kJ/mol or less. The anode active material for a lithium secondary battery has a high capacity, and thus, is useful in fabricating a high-capacity lithium secondary battery. Also, the anode active material for a lithium secondary battery has a small crystal size of a silicon phase and consequently a small change in volume during charging/discharging, and thus, ensures excellent cycle life characteristics in applications to batteries.