Accumulated evidence has established that aberrant regulation of histone deacetylases (HDACs) is one of the major causes of the development of human malignancies. Among different iso‐enzymes of HDAC and sirtuins grouped as the HDAC super family, little is known as to how histone deacetylase 2 (HDAC2) causes carcinogenesis in solid tumors. Here, in order to investigate the possible role of HDAC2 in gastric carcinogenesis, we analyzed the expression of HDAC2 in 71 gastric adenocarcinomas by immunohistochemistry. Moderate to strong expression of HDAC2 was found in 44 (62%) out of a total of 71 tumors. The majority of positive tumors, which were detected in the nucleus but not in normal gastric epithelium, did not express HDAC2 or showed only weak positive staining. Interestingly, we also noted that HDAC2 expression appeared to be associated with tumor aggressiveness as HDAC2 expression was observed to be statistically significant in advanced gastric cancer (P=0.0023, Chi‐square test) and in positive lymph node metastasis (P=0.0713, Chi‐square test). Taken together, these results suggest that HDAC2 may play an important role in the aggressiveness of gastric cancer.