Objective: To synthesize the evidence on the associations between vegetarian and vegan diets (VVDs) and eating disorder (ED) symptoms compared with omnivorous diets across the lifespan. Method: Following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) 2020 Guidelines, we searched PubMed, Scopus, Cochrane Library, PsycINFO, and Web of Science Databases up to May 1, 2026, with no language or date restrictions. Random effects models with the Hartung–Knapp–Sidik–Jonkman method were used to estimate pooled effect sizes (standardized mean difference [SMD] with 95% confidence interval [CIs]). Results: We included 24 cross-sectional studies with a total of 25,223 participants (67.7% female; mean age range: 14.9–49.6 years). ED symptoms did not differ significantly between participants who followed VVDs and those following omnivorous diets in analyses including all eligible studies (SMD = 0.07; 95% CI: −0.04 to 0.19; I2 = 80.3%; 95% prediction interval: −0.44 to 0.59). Results were unchanged when analyses were restricted to adult populations. No significant differences in ED symptoms were observed according to diet type (p = 0.524), measurement scale (p = 0.392), or geographic region (p = 0.633). In analyses restricted to adults, sex significantly moderated the pooled estimates (p = 0.028), with studies including a higher proportion of females reporting lower ED symptom scores among individuals following VVDs compared with omnivores. Discussion: ED symptom levels do not appear to differ significantly between individuals following VVDs and those following omnivorous diets. Longitudinal studies accounting for dietary quality, duration of adherence, dietary motivations, and psychosocial factors are also needed to clarify this association.