<p><i>Trichoglossum jejuense</i> is a recently described species known from a single locality on Jeju Island, South Korea. While some environmental samples of this species were reported from Taiwan based on the ITS region, no ascocarps have yet been found there. During research on fungi in Vietnam, a second world collection of <i>T. jejuense</i> was discovered. This collection expands our knowledge about the morphology, ecology, and distribution of this species. A comprehensive morphological study resulted in an extended description of <i>T. jejuense</i>, which is characterized by medium sized capitate ascocarps, 15-septate ascospores, and paraphyses with mostly straight or curved, moderately, or sparsely septate apical part and relatively long apical cells. <i>Trichoglossum jejuense</i> is compared with other morphological similar <i>Trichoglossum</i> taxa. In addition to the existing ITS sequences, LSU and <i>RPB</i>1 sequences have been generated for the first time for the species. According to the phylogenetic analysis, <i>T. jejuense</i> is placed within the <i>T. hirsutum</i> clade along with <i>T. benghalense</i>, <i>T. beninense</i>, <i>T. octopartitum</i>, <i>T. rasum</i>, <i>T. septatum</i>, <i>T. syamviswanathii</i>, and <i>T. variabile</i>.</p>