A multi-tier traction battery support assembly includes, among other things, a lower-tier battery array, an intermediate bracket directly secured to at least one endplate of the lower-tier battery array, and an upper-tier battery array supported on the intermediate bracket. A multi-tier traction battery support method includes supporting an intermediate bracket with at least one endplate of a lower-tier battery array and supporting an upper battery array with the intermediate bracket. The intermediate bracket is secured directly to the at least one endplate.