Signal transducer and activator of transcription 3 (STAT3) plays an important role in cancer cell proliferation. HO-3867, a STAT3 inhibitor, has shown preclinical efficacy in ovarian cancer, but there is limited data in Hepatocellular carcinoma (HCC), a lethal disease with limited systemic therapy options. This project hypothesizes HO-3867 inhibits HCC cellular proliferation through STAT3 inhibition. Methods: Effects of increasing concentrations of HO-3867 on three HCC cell lines were assessed via calorimetric assay. Cell lysates were examined via Western blot for cell cycle arrest, pro-and anti-apoptotic markers, and traditional oncogenic pathways Notch, STAT3, and Phosphatidylinositol-3 Kinase (PI3-K)/Akt. Results: Concentrations of 2 mM HO-3867 led to a significant reduction in cellular proliferation (p = 0.001). Upon Western analysis, HO-3867 was associated with increased expression of cell cycle markers p21 and p27 and reduction in cyclin D1. Furthermore, an increase in pro-apoptotic cleaved poly ADP ribose polymerase (PARP) and reduction in anti-apoptotic Bcl2, BclXL, XIAP, and Survivin was observed. HO-3867 also demonstrated a reduction in pSTAT3 and concomitant inhibition of Notch and PI3-K/ AKT pathways as evidenced by reduction in Notch1-3, Hes1, and pAKT. However, higher concentrations of HO-3867 were associated with increased phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), a cell survival protein. Conclusion: HO-3867, STAT3 inhibitor, mitigates HCC cell proliferation through cell cycle arrest and apoptosis through STAT3 inhibition. HO-3867 also reduces oncogenic targets Notch and Akt but at higher concentration increases phospho ERK1/2. This is the first study demonstrating HO-3867 effectiveness in HCC cells, providing a strong rationale for further preclinical analysis of HO-3867.