Provided are a positive active material for a lithium secondary battery, a method of preparing the positive active material, and a lithium ion secondary battery including the positive active material, the positive active material including a lithium-containing compound represented by the formula of Li2−xM′O3−y (wherein M′ is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, Ru, and F; 0≤x≤1; and 0≤y≤3) on a surface or inside of a lithium metal oxide represented by the formula of Li1−xNiyM1−yO2−z (wherein M is at least one element selected from Co and Mn; 0≤x≤0.05; 0.6≤y≤1; and 0≤z≤0.05).