Provided are a method for performing, by a first device, group cast communication with one or more second devices in a group, and a device for supporting same. The method may comprise the steps of: determining the number of physical sidelink feedback channel (PSFCH) resources associated with a physical sidelink shared channel (PSSCH) resource; on the basis of the number of PSFCH resources and the size of the group, determining a hybrid automatic repeat request (HARQ) feedback option; and transmitting, to the one or more second devices, information associated with the HARQ feedback option. Here, the HARQ feedback option can be any one of a first HARQ feedback option or a second HARQ feedback option.