Gastric cancer (GC) has a high morbidity and mortality, hence it is very important to elucidate the molecular pathogenesis mechanism of GC progression in order to find new treatment strategies. The present study aimed to explore the biological function of circular RNA_100395 (circRNA_100395) in GC. The expression level of circRNA_100395 in GC tissues, as well as normal epithelial cells and various gastric cancer cell lines, was detected using reverse transcription-quantitative PCR. Cell Counting Kit-8, EdU assay, flow cytometry and Transwell assays were performed to investigate cell proliferation, apoptosis, migration and invasion, respectively. A dual-luciferase reporter assay was performed to detect the correlation between circRNA_100395 and micro (mi)RNA-142-3p. Western blotting was performed to elucidate the potential regulatory mechanism. circRNA_100395 expression was found to be increased in GC tissues and cell lines. However, miR-142-3p expression was significantly reduced. Besides, low expression levels of circRNA_100395 were associated with poor tumor differentiation, advanced Tumor-Node-Metastasis stage, lymph node metastasis and shorter overall survival time. Moreover, overexpression of circRNA_100395 suppressed cell proliferation, increased the apoptosis rate and suppressed cell invasion and migration by inhibiting the PI3K/AKT signaling pathway. These findings also showed that miRNA-142-3p rescued the antitumor effects induced by circRNA_100395-overexpression. cirRNA_100395-overexpression had antitumor effects via regulating the miR-142-3p signaling pathway, which might be a promising treatment target for GC.