The p14ARF tumor suppressor is a key regulator of cellular proliferation and is frequently inactivated in human cancer. This tumor suppressor functions in the p53 and pRb cell cycle regulatory pathways and can effectively activate both pathways to induce growth arrest or cell death. We now report that p14ARF forms a complex with the E1A-regulated transcriptional repressor, p120E4F. p120E4F contacts p14ARF and p53 to form a ternary complex in vivo and enhances p14ARF-induced G2 cell cycle arrest in a p53-dependent manner. We suggest that the interaction of p14ARF and p120E4F forms an important link between the p14ARF and p53 tumor suppressor proteins, both of which exhibit enhanced cell cycle inhibitory activity in the presence of this transcriptional repressor.