Background: Acute pulmonary embolism (PE) is associated with a serious mortality rate. Thus, the rapid diagnosis and identification of patients at high risk of death is pivotal. The search for echocardiographic parameters for this purpose continues. Recent publications reveal correlations between myocardial longitudinal strain (LS) and body surface area (BSA). The aim of the study was to evaluate the usefulness of indexing the right ventricular (RV) speckle tracking LS to BSA in detecting PE and stratifying the risk of 30-day all-cause mortality. Methods: the prospective cross-sectional observational study group consisted of 167 consecutive patients (76 men, 45.5%) aged 69.5 ± 15.3 years, and they were referred for computed tomography pulmonary angiography. Patients underwent a transthoracic echocardiographic examination within 24 h of admission to the hospital ward. RVLS and their derivatives indexed to BSA were included in the analysis. Results: PE was confirmed in 88 patients, while 79 patients had no radiological features of PE. The only echocardiographic parameters that differed between subgroups were pulmonary flow acceleration (Act), McConnell’s sign, LS of the middle segment of the RV free wall, and its derivative indexed to BSA. During the 30-day follow-up of a subgroup of subjects with PE, 12 patients died. The mortality predictors with increasing prediction value included a RV free wall mid-segment LS (cut-off value: −21%, Area Under the Curve—AUC 0.6,p= 0.02) and its derivative indexed to BSA (−14 %/m2, AUC 0.62,p= 0.003), body mass index (24.7 kg/m2, AUC 0.63,p= 0.002), D-dimer serum concentration (3559 pg/mL, AUC 0.66,p< 0.001), Act (67 ms, AUC 0.67,p< 0.001), septal basal LS (−15%, AUC 0.68,p= 0.02), RV free wall basal segment LS (−14%, AUC 0.7,p= 0.015), age (66 years, AUC 0.74,p= 0.004), NT-proBNP (1120 pg/mL, AUC 0.75,p= 0.01), troponin T (66 ng/mL, AUC 0.78,p= 0.005), and the complex score of the Pulmonary Embolism Severity Index (AUC 0.88,p< 0.001). Conclusions: indexing of RVLS to BSA does not improve its prognostic value in patients with acute PE.