Hypoalbuminemia associates with poor acute ischemic stroke (AIS) outcomes. We hypothesised a non-linear relationship and aimed to systematically assess this association using prospective stroke data from the Norfolk and Norwich Stroke and TIA Register. Consecutive AIS patients aged ≥40 years admitted December 2003-December 2016 were included. Outcomes: In-hospital mortality, poor discharge, functional outcome (modified Rankin score 3-6), prolonged length of stay (PLoS) > 4 days, and long-term mortality. Restricted cubic spline regressions investigated the albumin-outcome relationship. We updated a systematic review (PubMed, Scopus, and Embase databases, January 2020-June 2023) and undertook a meta-analysis. A total of 9979 patients were included; mean age (standard deviation) = 78.3 (11.2) years; mean serum albumin 36.69 g/L (5.38). Compared to the cohort median, albumin < 37 g/L associated with up to two-fold higher long-term mortality (HR ; 95% CI = 2.01; 1.61-2.49) and in-hospital mortality (RR ; 95% CI = 1.48; 1.21-1.80). Albumin > 44 g/L associated with up to 12% higher long-term mortality (HR 1.12; 1.06-1.19). Nine studies met our inclusion criteria totalling 23,597 patients. Low albumin associated with increased risk of long-term mortality (two studies; relative risk 1.57 (95% CI 1.11-2.22; = 81.28)), as did low-normal albumin (RR 1.10 (95% CI 1.01-1.20; = 0.00)). Strong evidence indicates increased long-term mortality in AIS patients with low or low-normal albumin on admission.