PURPOSE: To assess mid-term survivorship of meniscal allograft transplantation (MAT) and determine the effect that pre-operative meniscal sizing has upon functional outcome and mechanical survivorship. METHODS: A prospectively collected database of patients receiving MAT from 2001 to 2017 was analysed. Data include demographics; sizing measurements, complications, further surgery, and patient-reported outcome measures (PROMs). Allografts were fresh frozen, non-irradiated, and sized using the Pollard technique. RESULTS: Seventy-three MATs were performed in 67 patients; mean age at MAT was 34 years (range 14-52 years). 56% were male and 62% were medial. The mean follow-up was 75 months (6.25 years). Mechanical survival at 5 and 10 years was 96% and 89.4%, respectively. There were statistically significant improvements in all PROMs; mean Lysholm score improved by 17.5 points [95% confidence interval (CI) 22.2-12.9, p < 0.001]; mean IKDC score improved significantly by 13.3 points (CI 19.3-7.4, p < 0.001); mean OKS improved by 5.6 points (CI 9.2-2.2, p < 0.002); and the median Tegner improved by 1 point. Forty-one MATs (56%) were undersized for width (range 1-11 mm). Seven MATs (10%) were undersized for length (range 1-4 mm). There was no statistically significant difference in mechanical survivorship or clinical outcomes between undersized, matched, or oversized grafts overall; however, sub-group analysis demonstrated increased failure when allografts were undersized by more than 5 mm in width. CONCLUSIONS: MAT is an effective treatment to improve function and alleviate pain with excellent survivorship in this series. Accepting an allograft that is more than 5 mm smaller in width than pre-operative templating increases the likelihood of clinical and mechanical failure. We, therefore, urge surgeons to be familiar with the measuring process used by their individual tissue bank provider to avoid graft-host mismatch that could affect outcome.