LncRNA H19 is a carcinogenic gene located at 11p15.5 of human chromosome, which is abnormally expressed in some types of tumors and acts as a tumor suppressor gene (TSG). Early diagnosis of breast cancer is crucial for patient treatment and prognosis. Long non coding RNA have potential roles in tumor initiation and differentiation. Aim: the objective of this study was to investigate whether circulating LncRNA H19 could be used as a biomarker in diagnosis of breast cancer. Besides we aimed at evaluating the association of LncRNA H19 with TNM staging in order to predict cancer prognosis. Methods: This prospective case-control study was carried out in Clinical Pathology Department and General Surgery Department, Faculty of Medicine-Zagazig University. The study included eighteen apparently healthy females attending outpatient laboratory (Group A) and 36 adult female patients, were classified into 2 groups: Group B included eighteen adult female patients newly diagnosed with breast cancer, admitted to General Surgery Department diagnosed by both mammography and histological examination of biopsy samples and Group C, included eighteen adult female patients with benign breast lesions. LncRNA H19 was assessed in plasma using quantitative real-time polymerase chain reaction (RT-PCR) on applied bio system. Results: circulating long non coding RNA H-19 was significantly higher among studied BC cases than healthy controls or cases with benign breast lesions. A significant increase was found in expression level of circulating H-19 among BC cases with TNM stages III/IV, tumor grades II and III and also those who had positive ER\PR expression. The expression level of long non coding RNA H-19 were used to discriminate breast cancer patients from controls and benign breast lesions with an AUC 0.931 with sensitivity 83.3% and specificity 86.1%. However CA15-3 had a sensitivity and specificity (77.8% and 80.7% respectively). Moreover, long non coding RNA H19 showed better performance in differentiation between TNM stages (I/II) and (III/IV) with sensitivity of 74.3% and specificity 82.8% versus CA15-3 sensitivity 71.4% and specificity 75.9% . Conclusion: Plasma H19 expression levels were up regulated in patients with BC. Moreover, long non coding RNA H19 showed better performance than CA15-3 in diagnosis and prognosis of breast cancer differentiating early stages I/II from late stages III/IV. Thus it could be used as promising biomarker in diagnosis and prognosis of breast cancer.