Provided are a cathode active material including lithium transition metal phosphate particles, including a first secondary particle formed by agglomeration of two or more first primary particles, and a second secondary particle formed by agglomeration of two or more second primary particles in the first secondary particle, and a method of preparing the same.Since the cathode active material may include first and second primary particles having different average particle diameters, the exfoliation of the cathode active material from a cathode collector may be minimized and performance characteristics, such as high output characteristics and an increase in available capacity, of a secondary battery may be further improved.