Glioblastoma (GBM) remains as the most common and aggressive brain tumor. The survival of GBM has been linked to the aberrant activation of swelling‐induced chloride current ICl,swell. In this study, we investigated the effects of ICl,swell on cell viability, proliferation, and migration in the human GBM cell lines, U251 and U87, using a combination of patch clamp electrophysiology, MTT, colony formation, wound healing assays and Western immunoblotting. First, we showed that the specific inhibitor of ICl,swell, DCPIB, potently reduced the ICl,swell in U87 cells. Next, in both U87 and U251 cells, we found that DCPIB reduced GBM viability, proliferation, colony formation, migration, and invasion. In addition, our Western immunoblot assay showed that DCPIB‐treated U251 cells had a reduction in JAK2, STAT3, and Akt phosphorylation, thus, suggesting that DCPIB potentially suppresses GBM functions through inhibition of the JAK2/STAT3 and PI3K/Akt signaling pathways. Therefore, the ICl,swell may be a potential drug target for GBM.