Open AccessCancer biomarker has increased tremendously providing great opportunities for improving the management of cancer patients by enhancing the efficiency of detection and efficacy of treatment. Every cell type has a unique molecular signature, referred to as biomarkers, which are identifiable characteristics such as levels or activities of a numerous of genes, proteins or other molecular features. Biomarkers are therefore, an objective measure or assessment of normal biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention. In cancer Biomarker refers to a substance that is indicative of the presence of cancer in the body. Telomerase activity is readily detected in most cancer biopsies, but not in premalignant lesion or in normal tissue samples with a few exceptions that include germ cells and hemopoietic stem cells. Telomere activity may therefore be a useful biomarker for diagnosis of malignancies and a target for inactivation in chemotherapy and gene therapy. The present review provides a brief account on telomerase as a biomarker for diagnosis of cancer.