Objectives <p>Repetitive head impacts from soccer heading may cause subclinical brain alterations, but the magnitude and consistency of neuroimaging abnormalities remain uncertain.</p> Methods <p>A systematic review and meta-analysis of brain MRI studies in soccer players was performed. Diffusion MRI was the primary outcome; magnetic resonance spectroscopy (MRS) and structural MRI morphometry were secondary outcomes.</p> Results <p>Thirteen independent studies were included. Five diffusion MRI studies (n≈300 players) were synthesised using Fisher’s z. Soccer heading exposure was associated with significant white-matter microstructural alteration (pooled Fisher’s z − 0.73, 95% CI − 1.02 to − 0.44), corresponding to an equivalent correlation of r≈ − 0.62 and a standard mean difference of approximately − 1.5. Between-study heterogeneity was moderate (I²≈68%). Individual studies reported increased radial or axial diffusivity (Hedges g up to + 3.00) or reduced fractional anisotropy (z range − 0.27 to − 1.40).</p> <p>Four morphometry studies showed small, non-significant differences in cortical thickness or volume (pooled Hedges g − 0.10, 95% CI − 0.22 to 0.10). Four MRS studies demonstrated predominantly increased choline- and myo-inositol–related metabolites (Hedges g ≈0·3–0·8), with minimal or inconsistent N-acetylaspartate change.</p> Conclusions <p>Soccer heading is associated with moderate-to-large effect sizes in diffusion MRI metrics of white-matter microstructure, whereas metabolic and structural MRI findings are smaller, less consistent, and of uncertain clinical significance.</p> Advances in knowledge <p>This meta-analysis provides the first quantitative evidence that soccer heading is associated with a robust, moderate-to-large diffusion MRI signal of white-matter microstructural alteration. It further shows that diffusion MRI is more sensitive than spectroscopy or structural morphometry for detecting subclinical brain effects of repetitive head impacts.</p>