This meta-analysis examined the predictive value of admission serum and urine carboxypeptidase-B activation peptide (CAPAP) in patients with severe acute pancreatitis. PubMed, Embase, and the Cochrane Library were searched for relevant studies published up to February 21, 2022. Seven studies (439 acute pancreatitis patients) were included. The summary sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), the area under the receiver operating characteristic curve (AUC) of admission serum CAPAP were 0.86 (95%CI: 0.76-0.93), 0.78 (95%CI: 0.68-0.85), 3.89 (95%CI: 2.56-5.91), 0.18 (95%CI: 0.09-0.33), 18.56 (95%CI: 6.99-49.30), and 0.90 (95%CI: 0.87-0.92), respectively; these values for admission urine CAPAP were 0.82 (95%CI: 0.50-0.95), 0.78 (95%CI: 0.68-0.86), 3.75 (95%CI: 2.40-5.85), 0.23 (95%CI: 0.07-0.79), 9.87 (95%CI: 3.71-26.22), and 0.84 (95%CI: 0.80-0.87), respectively. There were no significant differences between admission serum and urine CAPAP in sensitivity (1.05, 95%CI: 0.75-1.47; P = 0.781), specificity (1.00, 95%CI: 0.85-1.18; P = 1.000), PLR (1.04, 95%CI: 0.56-1.91; P = 0.906), NLR (0.78, 95%CI: 0.20-3.10; P = 0.727), and DOR (1.88, 95%CI: 0.47-7.49; P = 0.370). The AUC of serum CAPAP (1.07, 95%: 1.02-1.13; P = 0.007) was higher than that of urine CAPAP in predicting acute pancreatitis severity. Both admission serum and urine CAPAP had moderate predictive values for assessing the severity of acute pancreatitis. Key highlights Both admission serum and urine carboxypeptidase-B activation peptide (CAPAP) had moderate predictive values for assessing the severity of acute pancreatitis. The predictive value of admission serum CAPAP was higher than that of admission urine CAPAP in predicting acute pancreatitis severity. Including the measurement of serum CAPAP at admission in patients with suspected pancreatitis could help triage the patients and determine the course of management. Hospital policymakers could consider including it among the routine tests at admission for such patients.