Background <p>Active surveillance (AS) for low-risk papillary thyroid carcinoma (PTC) has been practiced for over 30 years with encouraging results globally. However, its adoption remains limited in certain contexts. This study aimed to evaluate the long-term oncological outcomes of patients undergoing AS and compare changes in the acceptance and discontinuation rates in Argentina over the past decade.</p> Methods <p>This prospective, observational cohort study (2014–2024) included 358 patients diagnosed with low-risk PTC measuring ≤1.5 cm across two university hospitals. Of these, 104 patients (29%) opted for AS and were followed up with thyroid ultrasounds and function tests annually for at least 24 months. Surgery was recommended for tumors showing a ≥3 mm increase in size, newly detected foci, or metastatic involvement. Outcomes were analyzed in two distinct phases: 2014–2019 (A) and 2020–2024 (B).</p> Results <p>Of the 104 patients under AS, 10.6% developed tumor growth of ≥3 mm, and 7.6% developed new PTC foci. The 5- and 10-year cumulative incidence of tumor growth was 7 and 8%, respectively. Lymph node metastases occurred in 0.9%. AS acceptance rates remained stable between Phase A (25%) and Phase B (30%) (<i>p</i> = 0.82). AS discontinuation rates were also similar: 19.5% in A and 12.6% in B (<i>p</i> = 0.63). Among patients discontinuing AS due to tumor progression, 31% underwent surgery. Anxiety was the main reason for surgery in 66% of cases in Phase A and 40% in Phase B. Lobectomies increased from 1.5% (A) to 9% (B, <i>p</i> = 0.8). No evidence of disease was achieved in 84% of cases at the end of follow-up.</p> Conclusions <p>Despite persistently low acceptance and adherence to AS, the long-term outcomes observed in this prospective study reinforce this approach as a feasible initial management option for low-risk PTC. These findings underscore the need for further efforts to improve the acceptance of AS among eligible patients.</p>