Disclosed are a method for transmitting and receiving downlink data in a wireless communication system, and an apparatus therefor. Specifically, a method for receiving downlink data from multiple cells in a wireless communication system may comprise a step for receiving downlink data on a physical downlink shared channel (PDSCH), wherein the PDSCH includes a first resource block group and a second resource block group, downlink data transmitted from a first cell is mapped to the first resource block group, downlink data transmitted from a second cell is mapped to the second resource block group, and a quasi-co-location (QCL) assumption is independently applied in order to decode the first resource block group and the second resource block group.