Gastric cancer (GC) is one of the most common malignancies and a leading cause of cancer-related death worldwide. Accumulating evidence reported that microRNA (miR)-133a was involved in GC. This study aimed to investigate the function and mechanism of miR-133a in the development and progression of GC. The expression of miR-133a and presenilin 1 (PSEN1) in two GC cell lines, SGC-7901 and BGC-823, were inhibited and overexpressed by transient transfections. Thereafter, cell viability, migration, and apoptosis were measured by trypan blue exclusion assay, transwell migration assay, and flow cytometry assay, respectively. Dual-luciferase reporter assay was conducted to verify whether PSEN1 was a direct target of miR-133a. Furthermore, quantitative real-time polymerase chain reaction and Western blot analysis were mainly performed to assess the expression changes of epithelial-mesenchymal transition (EMT)-associated proteins, apoptosis-related proteins, and Notch pathway proteins. MiR-133a inhibitor significantly increased cell viability and migration, while miR-133a mimic decreased cell viability, migration, and induced apoptosis. miR-133a suppression accelerated transforming growth factor-β1 (TGF-β1)-induce EMT, as evidenced by upregulation of E-cadherin, and downregulation of N-cadherin, vimentin, and Slug. Of contrast, miR-133a overexpression blocked TGF-β1-induce EMT by altering these factors. PSEN1 was a direct target of miR-133a, and suppression of PSEN1 abolished the promoting functions of miR-133 suppression on cell growth and metastasis. Moreover, PSEN1 inhibition decreased Notch 1, Notch 2, and Notch 3 protein expressions. This study demonstrates an antigrowth and antimetastasis role of miR-133a in GC cells. Additionally, miR-133a acts as a tumor suppressor may be via targeting PSEN1.