Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a sidelink transmitting (Tx) mobile station may perform a sub-band channel access in candidate frequency resources of an unlicensed band for a sidelink positioning reference signal (PRS) transmission to occur in time resources. The Tx may transmit, from the sidelink Tx mobile station to a sidelink receiving (Rx) mobile station, the sidelink PRS transmission in one or more sub-bands of the unlicensed band that have passed the sub-band channel access. Numerous other aspects are described.