A new spionid polychaete, Scolelepis (Parascolelepis) brunnea sp. nov., from an intertidal mud flat in Korean waters, is reported. The new species is unique among species of Scolelepis Blainville, 1828 in having conspicuously long, reddish-brown branchiae on the anteriormost chaetigers. The new species is morphologically and genetically most closely related to Scolelepis (Parascolelepis) anterobranchiata Lee and Min, 2022 from Korea. However, the new species differs from the latter by a combination of the following characteristics: presence of reddish-brown pigmentations on anteriormost body, neuropodial hooded hooks appearing from chaetigers 21 to 22, larger size of worms, and three teeth above the main fang of neuropodial hooded hooks. Detailed description and images of the new species, along with three gene regions (cytochrome c oxidase subunit I [COI], 16S ribosomal DNA [16S rDNA], and 18S rDNA), are provided.