Background: Postoperative infections are common in elective colorectal surgery (CRS). Perioperative probiotics/synbiotics have been investigated as a strategy to optimise the intestinal microbiota and reduce postoperative infections. The aim of this study was to conduct a systematic review and meta-analysis on the efficacy of perioperative probiotics/synbiotics on postoperative infection rates in elective CRS. Methods: Six databases were searched on 7th February 2023. Randomised controlled trials (RCTs) involving perioperative administration of probiotics/synbiotics among patients undergoing elective CRS for malignant and benign disease were included. The primary outcome was total postoperative infection rates within 30 days of surgery. Results: Twenty-eight RCTs, involving 2686 participants, demonstrated a reduction in total postoperative infections (RR 0.55, 95% CI 0.14 to 0.74, p < 0.0001), pneumonia (RR 0.43, 95% CI 0.29 to 0.66, p = 0.0001), UTIs (RR 0.54, 95% CI 0.32 to 0.94, p = 0.03), wound infections (RR 0.64, 95% CI 0.51 to 0.81, p = 0.0002) and line infections (RR 0.34, 95% CI 0.15 to 0.74, p = 0.007). Conclusion: Perioperative probiotics/synbiotics are associated with a reduction in total postoperative infection rates. Conclusions are limited by heterogeneity within the patient cohort and variability in intervention. Further investigation into optimal regimens is essential before clinical practice implementation.