Background: Colorectal cancer (CRC) is prevalent in Aotearoa (NZ), where surgery is the primary treatment. Anastomotic leakage (AL) is a significant surgical complication. Anastomotic reinforcement has been proposed to reduce AL, but its effectiveness remains inconclusive. Aims: Record anastomotic reinforcement practices in Australia and NZ, examine AL rates in patients with no, partial, or complete reinforcement, and assess whether reinforcement benefits specific colon regions (i.e., colon or rectum). Methods: Analyse data from CSSANZ Bowel Cancer Outcomes Registry (BCOR), covering colon and rectal cancer surgeries between July 2007 and December 2023. Patient demographics, preoperative factors, and postoperative complications, including AL, were analysed using logistic regression to adjust for confounders. Results: Among 26,427 cases, 46% had no reinforcement, 43% partial reinforcement, and 11% complete reinforcement. AL occurred in 4% of cases, with the highest rates in rectal anastomoses with partial reinforcement (7.5%). Colon anastomoses showed consistently low AL rates (~3%) regardless of reinforcement type. Adjusted regression analysis indicated partial reinforcement increased AL risk in rectal anastomoses (OR 1.4, CI 1.11–1.88), while complete reinforcement reduced AL risk (OR 0.62, CI 0.1–2.03), though not statistically significant. Conclusion: These findings indicate that anastomotic reinforcement of colon anastomoses is not associated with a reduction in anastomotic leakage (AL). Partial reinforcement, may increase risk of AL in rectal anastomoses. However, limited use of reinforcement in rectal cases restricts statistical power. A prospective study with a larger dataset is required to establish a causal relationship.