We aimed to investigate the correlation between serum laminin (LN) levels and cardiac function in patients with atrial fibrillation (AF) and its predictive value for in-hospital prognosis. This study included 295 patients with AF who were admitted to the Second Affiliated Hospital of Nantong University from January 2019 to January 2021. The patients were divided into three groups according to the New York Heart Association (NYHA) functional classification (I-II, III, and IV); the LN levels increased with increasing NYHA class (P < 0.05). Spearman's correlation analysis revealed a positive correlation between LN and NT-proBNP (r = 0.527, P < 0.001). Of the patients, 36 had in-hospital major adverse cardiac events (MACEs), of whom 30 had acute heart failure, 5 had malignant arrhythmias, and one had stroke. The area under the ROC curve for predicting the in-hospital MACEs by LN was 0.815 (95% CI: 0.740-0.890, P < 0.001). Multivariate logistic regression analysis revealed that LN could be an independent predictor of in-hospital MACEs (odds ratio: 1.009, 95% confidence interval: 1.004-1.015, P = 0.001). In conclusion, LN may serve as a potential biomarker to evaluate the severity of cardiac function and predict in-hospital prognosis in AF patients.