Gundelia (G.) tournefortii has antibacterial, anti-inflammatory, and hypolipemic effects. We evaluated the anticancer effect of G. tournefortii in an hepatocellular carcinoma (HCC) mouse model of an HCC cell line (Hep3B) injected into NOD.CB17-Prkdc-SCID/NCrHsD male mice. Tumorigenicity was assessed by tumor size, histology, serum α-fetoprotein (αFP), and glypican 3 (GPC3). HCC-related gene expression of the cell cycle (Cyclin-dependent kinase inhibitor 2A (CDNK2A)), proliferation (MKI67), and platelet-derived growth factor receptor α (PDGFA) were measured. HCC cell cycle alterations, apoptosis, and antioxidant markers in serum and liver following treatment with G. tournefortii were determined. Signaling pathways of liver p53 and phosphorylated PI3K, AKT, and mTOR were also evaluated. Results indicate a significant increase in tumor size in HCC animals associated with elevated αFP, GPC3, and MKI67. Tumor markers of p53 and phosphorylated AKT/PI3K/mTOR signaling pathway were diminished, with less proliferating cells and reduced PDGFRA gene expression following G. tournefortii infection. H&E staining showed a remarkable reduction in inflammatory lesions in HCC mice treated with G. tournefortii. This result was in line with a significant delay in the G2/M phase of HCC-primary hepatocytes by 1.39- to 2.4-fold and reduced HCC necrosis associated with inhibited CDNK2A gene expression. Antioxidant activity was significantly lower in the HCC mice than in the control group. Moreover, G. tournefortii inhibited the HCC formation of 3D MCTS spheroids. G. tournefortii treatment markedly restored antioxidant levels and displayed anticancer and antiproliferative effects and could be a promising cancer therapy.