Background and Objectives:Anti-CGRP (receptor) antibodies are approved as preventive treatment for migraine. Recent concerns have been raised after a retrospective analysis of post-marketing case reports of elevated BP associated with erenumab. In this prospective follow-up study we aimed to assess the safety regarding blood pressure (BP) in a real world setting.Methods:All people with migraine that were treated with erenumab and fremanezumab at the Leiden Headache Center between January 2019 and January 2021 were included. BP measurements were collected from baseline (T0) until 12 months follow-up, with a three-month interval (T1–T4). Mixed linear models were fitted with time as a fixed effect and the patient as a random effect.Results:Both systolic and diastolic BP were increased at all time points T1-T4 compared to T0 (p<0.001). The maximum estimated increase in mean systolic BP was 5.2 mmHg (95% CI: 3.1-7.5). The maximum estimated increase in mean diastolic BP was 3.5 mmHg (95% CI: 2.0-4.9). In the erenumab group (n = 109), both systolic and diastolic BP were increased all time points compared to T0 (all p<0.001). For fremanezumab (n = 87), systolic but not diastolic BP was increased compared to T0 at T1 (p=0.006) and T2 (p=0.004). Four patients (3.7%) with normal BP at T0 required antihypertensive treatment after erenumab was started.Discussion:The mean systolic and diastolic BP increased after anti-CGRP (receptor) antibodies were started. The majority of patients remained within the normal blood pressure limits, but some patients required antihypertensive treatment. Physicians should be aware that people with migraine may be at risk to develop hypertension when treated with anti-CGRP (receptor) antibodies and this should be added to (inter)national treatment guidelines.Classification of Evidence:This study provides Class III evidence that anti-CGRP (receptor) antibodies increase blood pressure when used to treat patients with migraine.