A method for performing wireless communication by a first device and a device for supporting same are provided. The method may include receiving, from a second device, a physical sidelink control channel (PSCCH) including a first sidelink control information (SCI) for scheduling a physical sidelink shared channel (PSSCH); receiving, from the second device, the PSSCH including a second SCI; and transmitting, to the second device, a hybrid automatic repeat request (HARQ) feedback through a physical sidelink feedback channel (PSFCH) in response to the PSSCH based on a format of the second SCI.