Disclosed according to the present disclosure are a method for transmitting/receiving channel state information in a wireless communication system, and an apparatus therefor. Method for reporting channel state information by a user equipment comprises the steps of: receiving CSI reporting-related configuration information; wherein a report for at least one of aperiodic CSI, periodic CSI, or semi-persistent CSI is configured based on the CSI reporting-related configuration information, calculating first information and second information for a channel quality; wherein the first information is calculated by applying a precoding matrix indicator (PMI) included in latest aperiodically reported CSI, and the second information is calculated by applying the PMI at a time of calculation of the second information, and determining at least one of whether to transmit a flag and a value of the flag; and transmitting CSI to the base station based on the first information and the flag.