Despite 250 years of taxonomic classification and over 1.2 million species already catalogued, known species diversity is only a small part of true species diversity on Earth, and thus, the known species are only the tip of iceberg. Here, we investigated the genus Pholcus Walckenaer, 1805 of the family Pholcidae C. L. Koch, 1850 in the Changbai Mountains, Northeast China, which provides an excellent case of high species diversity. Previously, only 14 endemic Pholcus spiders, all belonging to the P. phungiformes species group, and two introduced species P. manueli Gertsch, 1937 and P. zichyi Kulczyński, 1901 from the P. crypticolens species group, have been recorded from this area. Our study confirmed 11 new species of the P. phungiformes species group based on morphology and three methods of molecular species delimitation: P. gaizhou Yao & Li, sp. nov. , P. guanshui Yao & Li, sp. nov. , P. jiguanshan Yao & Li, sp. nov. , P. longxigu Yao & Li, sp. nov. , P. luoquanbei Yao & Li, sp. nov. , P. shenshi Yao & Li, sp. nov. , P. tianmenshan Yao & Li, sp. nov. , P. wangjiang Yao & Li, sp. nov. , P. xingqi Yao & Li, sp. nov. , P. yaoshan Yao & Li, sp. nov. , and P. yuhuangshan Yao & Li, sp. nov. This study brings the fauna of the P. phungiformes species group from the Changbai Mountains to 25 species, approximately two times more than previously known, which could indicate that species diversity in the area is underestimated for all arthropod fauna.