Objective: Development of gastric carcinoma is regulated by many factors. Adenine-thymine rich interactive domain 1A (ARID1A) is a tumour suppressor gene involved in chromatin remodeling and it encodes the ARID1A protein.Recent studies have shown the loss of ARID1A expression in gastric carcinomas may have a prognostic significance.In our study, we investigated the possible prognostic role of ARID1A loss in gastric carcinomas.Method: We investigated ARID1A expression in 113 formalin-fixed, paraffin-embedded gastric carcinoma specimens and its association with different pathological and clinical parameters.Results: The mean percentage of ARID1A-stained cells was 55.42% (min 1%, and max 100%). ARID1A expressionwas found in pT1b (73.89%), pT254 (22%), pT353 (76%) and pT4 (53.92%) tumours (p=0.219). ARID1A expressionwas found in poorly cohesive (56.61%), tubular (48.52%), mucinous (80%), papillary (73.75%) and mixed type(76.25%) tumours (p=0.093). ARID1A expression was found in HER2-positive (61.23%) and HER2-negative (53.22%)tumours (p=0.262). ARID1A expression was evaluated and compared with tumour localisation and other pathological parameters as lymph node metastasis, perineuronal invasion, lymphovascular invasion, and any statisticallysignificant difference was not found between both groups. Contrarily, there was a significant association betweenARID1A expression and survival of HER2 negative tumors (p=0.047).Conclusion: Identification of specific biomarkers is very important for prediction of clinical outcome in gastrictumours. We demonstrated loss of ARID1A expression in HER2-negative gastric carcinomas positively correlatedwith overall survival. These results suggest that ARID1A may play a role in the biology of HER2-negative gastriccarcinomas.