Background <p>Although recent research suggests that regulatory T (Treg) cells may be involved in migraine pathophysiology, no review has provided a comprehensive assessment of their levels in this condition. This systematic review and meta-analysis aims to assess Treg levels in migraine patients.</p> Methods <p>We systematically searched PubMed, Embase and Cochrane on July 5, 2024 (updated on March 19, 2026), and included all original studies providing data on Treg levels in migraine.</p> Results <p>Among 1,162 studies identified, five were included in the narrative review and four in the meta-analysis. Data were pooled using a random-effects model. Standardized mean differences (SMD) were calculated to compare peripheral whole blood Treg levels between migraine and control groups. Our narrative review showed decreased Treg levels in three of five studies comparing migraine patients and controls, and in two of three studies on interictal episodic migraine patients and controls. Our meta-analysis of few but carefully selected data suggested a significant decrease in Treg cell levels in migraine (SMD − 4.21 [-7.76; -0.66], <i>p</i> = 0.02, I²=98.3%).</p> Conclusions <p>Our findings suggest Treg levels are decreased in migraine and of potential interest in understanding migraine pathophysiology. However, the limited data available warrant further investigations to shed light on their relevance and therapeutic potential in this condition.</p> Trial registration <p>PROSPERO CRD42023490445.</p> Clinical trial number <p>Not applicable.</p>