Restoring large posterior vital-teeth cavities remains a clinical challenge. This systematic review and meta-analysis aimed to compare the clinical performance of short fiber-reinforced composites (SFRCs) versus conventional resin-based composites (RBCs) in such cavities. PubMed, Web of Science, and Scopus were searched, identifying 1,632 records. Five randomized controlled trials met inclusion criteria for qualitative synthesis, and four were included in the meta-analysis. Risk of bias was assessed using Cochrane RoB 2.0, and the certainty of evidence was rated via GRADE. Meta-analysis showed no statistically significant difference between SFRCs and conventional RBCs across different clinical parameters following the USPHS criteria. Sensitivity analyses addressed heterogeneity in color match (RR=0.77; 95% CI 0.57–1.03; P=0.08; I² = 80%) and marginal adaptation (RR=1.10; 95% CI 0.91–1.33; P=0.32; I² = 70%). However, sensitivity analysis suggested a possible advantage for RBCs in terms of color match (RR=0.68; 95% CI 0.55–0.83; P=0.0001), these findings are based on a limited number of studies and should be interpreted cautiously. Overall, the certainty of evidence was low, with two trials judged at high risk of bias, two at low risk, and one with some concerns. Current low-certainty evidence suggests that SFRCs perform comparably to conventional RBCs in large posterior cavities. However, given the limited number of trials and variable study quality, these results should be interpreted cautiously. Further high-quality, long-term RCTs are needed to confirm these findings.