A composite positive active material includes: a composite including a first metal oxide represented by Formula 1 and having a layered structure, and a second metal oxide having at least one crystal structure selected from a layer structure, a perovskite structure, a rock salt structure, and a spinel structure, wherein a content of the second metal oxide is greater than 0 and equal to or less than 0.2 moles, per mole of the composite, LiNixM11-xO2-eM2e  Formula 1 wherein, in Formula 1, M1 is at least one element selected from Group 4 to Group 14 of the Periodic Table of the Elements; Ma is at least one element selected from F, S, Cl, and Br; 0.7≤x