BackgroundAt present, the relationship between severe acute pancreatitis (SAP) and albumin infusion is not clear. We aimed to identify the impact of serum albumin on the prognosis of SAP and the association between albumin infusions and mortality for hypoalbuminemia patients.MethodsThis was a retrospective cohort study that analyzed 1000 patients with SAP who were admitted to the First Affiliated Hospital of Nanchang University between January 2010 and December 2021 using data from a prospectively maintained database. Multivariate logistic regression analysis was conducted to reveal the relationship between serum albumin within 1 week after admission and poor prognosis of SAP. Propensity score matching (PSM) analysis was adopted to evaluate the effect of albumin infusion for hypoalbuminemia patients with SAP.ResultsThe prevalence of hypoalbuminemia (≤ 30 g/L) was 56.9% within 1 week after admission. Multivariate logistic regression identified that age (OR: 1.02; 95% CI: 1.00-1.04; P = 0.012), serum urea (OR: 1.08; 95% CI: 1.04–1.12; P < 0.001), serum calcium (OR: 0.27; 95% CI: 0.14–0.50; P < 0.001), lowest albumin level within 1 week after admission (OR: 0.93; 95% CI: 0.89–0.97; P = 0.002), and APACHE II score ≥ 15 (OR: 1.73; 95% CI: 1.19–2.51; P = 0.004) were independently associated with mortality. The PSM analysis demonstrated that mortality (OR: 0.52, 95% CI: 0.29–0.92, P = 0.023) was less common in albumin-infused than non-albumin-infused hypoalbuminemia patients. In subgroup analyses, doses > 100 g within 1 week after admission for hypoalbuminemia patients with albumin infusions was associated with lower mortality than doses ≤ 100 g (OR: 0.51, 95% CI: 0.28–0.90, P = 0.020).ConclusionsHypoalbuminemia in early-stage SAP is significantly related to poor prognosis. However, albumin infusions could significantly decrease mortality in hypoalbuminemia patients with SAP. Additionally, infusing sufficient albumin within a week after admission may decrease mortality in hypoalbuminemia patients.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12876-023-02801-8.