Polychaetes (Phylum Annelida) respond to sensory stimuli through the usage of sensory organs and appendages, such as palps, which vary in shape and structure depending on lifestyle. The typical palps of nereidid polychaetes are tapered appendages constituted by two articles. The palpophore is the wider and longer basal article, followed by the thinner and shorter palpostyle that contains the majority of sensory cells. Previous studies on Hediste diversicolor palps were focused on these sensory cells. To achieve a more comprehensive view of the histology and ultrastructure of the palps, H. diversicolor specimens were collected from the northern Portuguese Atlantic coast and the palps were processes for light (semithin sections) and transmission electron microscopy. The current study revealed details of the cuticle, which is thinner in the palpostyle than in the palpophore. Five types of secretory cells were distinguished mainly based on the characteristics of their secretory vesicles. Two of these types could be classified as protein-secreting cells, and the other three as mucus-secreting cells. Granulocytes and eleocytes were found in the celom cavity of the palps. The latter contained lipid droplets and a very large amount of glycogen. In the central region of the palpophore, a ring of muscle cells responsible for the retraction of the palpostyle encircled the main palp nerve. The latter was formed by numerous axons and glial cells containing bundles of filaments and gliosomes.