Background and Objective: Advanced thyroid cancer leads to worse overall survival and a higher risk of locoregional recurrence. Tyrosine kinase inhibitors have emerged as a management alternative in these conditions. However, serious adverse effects such as high blood pressure are common in clinical trials and real-life studies. The objective of this study was to evaluate the incidence of arterial hypertension in patients undergoing treatment for advanced thyroid cancer with the tyrosine kinase inhibitors lenvatinib Methods This is a retrospective cohort study of patients with advanced thyroid cancer being managed with Lenvatinib, a tyrosine kinase inhibitor. The incidence of arterial hypertension after the start of treatment was evaluated. Results Among the subjects included in the study (n=26), the mean age was 64.6 ±11.8; 57.7% were women and hypertension occurred in 88.5% (23/26), being CTCAE grade ≥ 3 in 43.5% (10/23). In 12 of 23 it occurred due to exacerbation of pre-existing hypertension and in 10 of 23 it corresponded to de novo hypertension induced by the drug. A patient presented grade 4 hypertension due to posterior reversible encephalopathy syndrome. 6 patients died during follow-up, all developed hypertension during treatment with Lenvatinib. Conclusions: High blood pressure is a common and early adverse effect in the management of advanced thyroid cancer with Lenvatinib. Management strategies to improve drug tolerability may improve disease outcomes, treatment adherence and patient-related outcomes.