A method by which a first device performs wireless communication, and a device for supporting same are provided. The method may comprise the steps of: transmitting, to a second device, through a physical sidelink control channel (PSCCH), first sidelink control information (SCI) for the scheduling of second sidelink control information (SCI) and a physical sidelink shared channel (PSSCH), the first SCI including information related to a frequency resource allocation, information related to a time resource allocation, and information related to the format of the second SCI; and transmitting, to the second device, through the PSSCH, an inter-UE coordination message and the second SCI including a source ID and a destination ID. The inter-UE coordination message can include information related to a preferred resource or information related to a non-preferred resource, and information indicating that the inter-UE coordination message has been transmitted can be included in the first SCI or the second SCI.