Adolescent and young adult (AYA, 15-39 years old) patients with papillary thyroid carcinoma (PTC) experience significant psychological distress and place great importance on obtaining information regarding the disease; however, their demands remain unmet. We aimed to investigate clinicopathological and molecular features of PTC in AYA patients and compare them to those of PTC in older patients (≥40 years). This retrospective study enrolled 1,677 patients diagnosed with PTC from January 2018 to December 2022, with 400 AYA patients and 1,277 older adults. At the time of diagnosis, AYA patients with PTC had higher rates of presentation in females, larger tumor size (>2.0 cm), lymphatic vessel invasion, chronic thyroiditis, clinical lymph node metastasis, and pathologic lymph node metastasis, but lower rates of multifocality and extrathyroidal extension compared with PTC in older adults. The two groups had no significant differences regarding surgical method and distant metastasis. The prevalences of BRAF p.V600E and TERT promoter mutations of PTC were significantly lower in AYA patients (69.1% vs. 82.6% and 1.3% vs. 18.8%, respectively; both p < 0.001). In conclusion, PTC in AYA patients differed from PTC in older patients. Particularly, BRAF p.V600E and TERT promoter mutations in AYA with PTC were less frequently observed than in older adults.