Gastric cancer (GC) is the second most frequent oncological cause of death, the ?fth most common malignancy in the world, and accounts for 6.8% of all tumors. As an aggressive disease, GC is often diagnosed at an advanced stage, which is why it is a major cause of cancer-related death. In the last several decades, the incidence of GC has decreased, which should be credited to advancements in diagnostic and therapeutic technologies including tumor marker detection systems, imaging modalities, pathological methods, gastroscopy, and particularly, surgical and pharmacologic interventions. Because they are economical, convenient and noninvasive, the detection of conventional serum tumor biomarkers, such as CEA, CA19-9 and CA72-4, has been widely employed in the diagnosis and evaluation of GC. However, due to their poor specificity and sensitivity, these molecular markers cannot meet the demand of early GC detection. Hence, new and reliable tumor biomarkers are desperately needed. This review systematically summarizes the three most commonly used biomarkers (CEA, CA19-9 and CA72-4) of GC and addresses two categories of potential molecular biomarkers for the diagnosis of GC: microRNA and methylated DNA.