Patients diagnosed with diffuse large B-cell lymphoma (DLBCL) are at increased risk of developing atrial fibrillation (AF). Abnormal P-wave parameters (PWPs) have been identified as independent predictors of AF, however, their prognostic significance in DLBCL patients remains unknown. Newly diagnosed DLBCL patients from January 2015 to August 2022 were retrospectively included in this study. Patients were devided as with abnormal PWPs or without it. Primary outcome was the all-cause mortality. The median duration of follow-up was 16.3 months. The Kaplan‒Meier method and multivariable COX proportional hazards regression models were used to analyze the relationship between PWPs and all-cause mortality. Logistic regression analyses were performed to identify risk factors associated with PWPs. A total of 374 newly diagnosed DLBCL patients were included, of whom 137 patients exhibited abnormalities in PWPs. Compared to the group with normal PWPs, patients with PWPs abnormalities had a higher proportion of males (p = 0.001), elevated levels of blood urea nitrogen (p = 0.038) and blood creatinine (p = 0.005), and a higher rate of all-cause mortality (p = 0.001). PWPs, particularly P-wave duration (p = 0.017) and P-wave terminal force in lead V1 (PTFV1) (p = 0.001), were independently correlated with all-cause mortality in DLBCL patients. Furthermore, male patients exhibited a higher susceptibility to abnormal PWPs (p = 0.001). PWPs, particularly P-wave duration and PTFV1, serve as simple yet effective prognostic indicators for all-cause mortality in DLBCL patients. Consequently, vigilant monitoring of PWPs, particularly in male patients, is warranted to accurately evaluate the prognosis of DLBCL.© 2024. The Author(s).