Provided are a method for a first device to perform wireless communication, and a device for supporting same. The method may include the steps of: transmitting first sidelink control information (SCI) on a first resource through a first physical sidelink control channel (PSCCH); transmitting second SCI on the first resource through a first physical sidelink shared channel (PSSCH) related to the first PSCCH, wherein at least one of the first SCI and the second SCI includes information related to a second resource, and a transport block (TB) is not transmitted through the first PSSCH; transmitting the first SCI on the second resource to a second device through a second PSCCH; and transmitting the second SCI and the TB on the second resource to the second device through a second PSSCH related to the second PSCCH.