Background: Prostate cancer (PC) is a malignant disease, which is common in men. Interleukin-6 (IL-6) mediates the progression of PC through PI3K/AKT, JAK-STAT, and ERK1/2 MAPKs signaling pathways. Gallic acid, a phenolic compound, has anti-oxidant, antiproliferative, and anti-tumorigenic properties. Objectives: This study was undertaken to evaluate the effects of gallic acid on DU-145 cell viability, proliferation, invasion, IL-6 gene expression, and the cellular levels of phosphorylated STAT3, ERK1/2, and AKT signaling proteins.