<p>To evaluate the diagnostic accuracy of global longitudinal strain (GLS) measured by two-dimensional speckle-tracking echocardiography (2D-STE) compared with cardiac magnetic resonance imaging (CMR) in patients with acute myocarditis. This systematic review and meta-analysis followed a PROSPERO-registered protocol (CRD42024563890) and adhered to the PRISMA 2020 guidelines. We searched PubMed, EMBASE, CENTRAL, ClinicalTrials.gov, and reference lists through 1 September 2024. Eligible studies enrolled patients with suspected acute myocarditis, confirmed by the Lake Louise CMR criteria, who underwent both 2D-STE and CMR, and reported diagnostic accuracy outcomes. Data extraction and risk-of-bias assessment were conducted independently by two reviewers using the QUADAS-2 tool. Pooled sensitivity and specificity were calculated using a random-effects model, with subgroup analyses according to the GLS cut-off value. Seven studies involving 441 adult patients were included in the analysis. The pooled sensitivity of GLS for diagnosing acute myocarditis was 0.79 (95% CI, 0.74–0.83), and the pooled specificity was 0.78 (95% CI, 0.72–0.83). Subgroup analysis revealed that a GLS cut-off value of greater than − 18% yielded the highest sensitivity (0.88; 95% CI, 0.80–0.93) and specificity (0.92; 95% CI, 0.85–0.96). Most studies (71.4%) had a low risk of bias. GLS assessment by 2D-STE demonstrates relatively high sensitivity and specificity for diagnosing acute myocarditis. It may serve as a complementary tool or supportive imaging modality in patients with suspected acute myocarditis. A GLS threshold around − 18% was reported in a limited number of studies; however, this observation should be interpreted cautiously given the small evidence base.</p> Graphical abstract <p></p>