The invention provides functionalized block composites and crystalline block composites as compatibilizers. In particular, the invention provides compositions of at least three polymers and a compatibilizer. The compatibilizer comprises a functionalized olefin-based polymer formed from at least (A) and (B): (A) a crystalline block composite comprising: a block copolymer comprising a propylene-based crystalline block and crystalline ethylene-based block; a propylene-based crystalline polymer; and, a crystalline ethylene-based polymer; and (B) at least one functionalization agent or a functionalized olefin-based polymer formed from at least (A) and (B): (A) a crystalline block composite comprising: a block copolymer comprising a propylene-based crystalline block and crystalline ethylene-based block; a propylene-based crystalline polymer; and, a crystalline ethylene-based polymer; and (B) at least one functionalization agent.