Objects To study the incidence of Delphian lymph node (DLN) metastasis in patients with unilateral pa-pillary thyroid carcinoma (PTC) and the clinical significance. Methods The clinicopathological data of 522 patients with unilateral PTC in our hospital between January 2016 and December 2019 were analyzed retrospectively. The association between DLN metastasis and the clinicopathological characteristics including age, sex, tumor size, multifocality, capsular invasion, extrathyroidal extension, tumor location, central lymph node (CLN) metastasis (excluding DLN), and lateral lymph node metastasis was analyzed. Results One hundred thirty-three(25.5%) of 522 patients had DLN metastasis. It was significant that DLN metastasis was associated with age (P=0.047), male (P<0.001), larger tumor size (P<0.001), capsular invasion (P<0.001), extrathyroidal extension (P=0.004), tumor location (P=0.003), CLN metastasis (P<0.001), number of positive CLN (excluding DLN) (P<0.001), lateral compartment lymph node (LLN) metastasis (P=0.036), number of positive LLN (P=0.004) and number of DLN removed (P=0.043). Conclusions The DLN metastasis was shown to be associated significantly with several factors of poor PTC prognosis. When the DLN of intraoperative frozen section is positive, careful dissection and evaluation of CLN and LLN are essential with necessary follow-up.