Specimens of a Neobisium (Pseudoscorpiones: Neobisiidae) were collected from Craig yr Aber woods, Bridgend, Wales, in November 2017. Using morphological characters and DNA barcoding of the cytochrome c oxidase subunit I gene they were identified as N. simile (L. Koch, 1873), a species new to Britain. Molecular comparison with other Neobisium specimens confirms N. simile as the most similar species (88% similarity) with which it forms a single clade, although the degree of dissimilarity could suggest an unrecognized sibling species. A detailed morphological description of N. simile from Craig yr Aber is provided, along with the DNA barcode, in view of the potential for future taxonomic revision. A probable record of N. simile from Wales in 1984 is discussed. Knowledge of the distribution and ecology of N. simile is summarized. The Welsh population of N. simile was probably introduced from the Pyrenees or south-western France, possibly with imports of raw materials for the steel industry. British pseudoscorpion workers should be vigilant for N. simile, though it may be restricted to South Wales.