Background/Objectives: Adherence to the Mediterranean diet (MedDiet) has been associated with numerous health benefits, yet it is often suboptimal among university students. Its relationship with academic performance (AP), an outcome with potential long-term implications, has not been quantitatively synthesized in this population. This study aimed to synthesize the available evidence on the associations between MedDiet adherence and AP in university students. Methods: A systematic review and meta-analysis followed PRISMA 2020 and MOOSE guidelines (PROSPERO: CRD42024526903). PubMed, Web of Science, Scopus, and the Cochrane Library were searched from inception to 6 August 2026. AP was examined through objective (grade point average, mean academic grade, or university entrance scores) and subjective measures (academic self-concept or perceived academic progress). Standardized mean differences (SMDs) were pooled using random-effects models. Subgroup, meta-regression, and sensitivity analyses were performed. Methodological quality was appraised with the NIH tool, and certainty of evidence with GRADE. Results: Twelve cross-sectional studies were included (10,931 students; study-level mean ages: 19.0–25.1 years; 56.7% female). A positive association was observed in the primary analysis of objective AP measures (10 studies; SMD = 0.49; 95% CI: 0.04 to 0.94; I2 = 98.2%) and for subjective measures (3 studies; SMD = 0.42; 95% CI: 0.14 to 0.71; I2 = 0.0%). The certainty of the evidence was very low. Conclusions: Higher MedDiet adherence may be associated with better AP in university students. However, considerable between-study heterogeneity and very low certainty of the evidence limit confidence in the pooled estimates. Further high-quality longitudinal and intervention studies are needed.