The NFIA-ETO2 fusion is the product of a t(1;16)(p31;q24) chromosomal translocation so far exclusively found in pediatric patients with pure erythroid leukemia (PEL). To address the role for the pathogenesis of the disease, we expressed the NFIA-ETO2 fusion in murine erythroblasts. We observed that NFIA-ETO2 significantly increased proliferation and impaired erythroid differentiation of murine erythroleuemia (MEL) cells and of primary fetal liver-derived erythroblasts. However, NFIA-ETO2-expressing erythroblasts acquired neither aberrant in vitro clonogenic activity nor disease-inducing potential upon transplantation into irradiated syngenic mice. In contrast, in the presence of one of the most prevalent erythroleukemia-associated mutations, TP53R248Q, expression of NFIA-ETO2 resulted in aberrant clonogenic activity, and induced a fully penetrant transplantable PEL-like disease in mice. Molecular studies support that NFIA-ETO2 interferes with erythroid differentiation by preferentially binding and repressing erythroid genes that contain NFI binding sites and/or are decorated by ETO2, resulting in a activity shift from GATA- to ETS-motif-containing target genes. In contrast, TP53R248Q does not affect erythroid differentiation but provides self-renewal and survival potential, mostly via downregulation of known TP53 targets. Collectively, our work indicates that NFIA-ETO2 initiates PEL by suppressing gene expression programs of terminal erythroid differentiation and cooperates with TP53 mutation to induce erythroleukemia.