Background: RNASEH2A, also known as ribonuclease H2 subunit A, plays a vital role in regulating tumorigenesis and progression. Nonetheless, our understanding of the biological roles of RNASEH2A in gastric cancer (GC) is still limited. Hence, this investigation aimed to explore the impact of RNASEH2A on various cellular processes, including proliferation, migration, invasion, and apoptosis, in GC cells derived from humans. Methods: RNASEH2A expression in GC tissues and cell lines was analyzed using the GEPIA database, immunohistochemistry, and immunocytochemistry. A total of 150 paired GC samples and adjacent normal tissues were collected for tissue microarray analysis. Various assays, including Cell Counting Kit-8 (CCK-8), scratch healing, transwell, western blotting, and Annexin V/Propidium iodide (PI) staining, were conducted to assess the influence of RNASEH2A on proliferation, migration, invasion, and apoptosis in GC cells. Results: The results showed that the expression level of RNASEH2A was upregulated in GC tissues and cells (p < 0.05). Furthermore, the T stage, N stage, cancer stage, and lymph node metastasis were positively correlated with RNASEH2A expression (p < 0.05). RNASEH2A silencing substantially decreased the proliferation, clone formation capacity, migration, and invasion, while increasing apoptosis in GC cells (p < 0.05). Conclusions: Our results indicate that RNASEH2A can promote GC cell proliferation, migration, and invasion, while inhibiting apoptosis, thereby contributing to the emergence of GC. RNASEH2A could be a therapeutic target for GC treatment strategies.