Background Matrix-metalloproteinase-9 (MMP-9) is expressed by a wide range of cells and plays a significant role in the regulation of the tumor microenvironment of various cancers including gastric cancer. This study aims at the correlation of MMP-9 expression in gastric cancer with existing prognostic factors. Methods The MMP-9 expression in gastric cancer was identified by immunohistochemistry using a monoclonal antibody in paraffin-embedded sections, correlated with various clinicopathological parameters, and statistically analyzed. Results MMP-9 expression in gastric cancer was significantly correlated with the grade, depth of invasion, and TNM stage (p-value = 0.003, 0.019, and 0.025, respectively). A significant difference in expression between tumor tissue and adjacent gastric mucosa (p-value = 0.000) was also observed. 100% negative expression was found in well-differentiated tumors and early gastric carcinoma (T1). Conclusion The study results suggest that MMP-9 expression could be a potential biomarker of aggressive gastric cancer and candidates for the possible diagnostic and prognostic tool.