Abstract Intrinsic and extrinsic cues determine developmental trajectories of hematopoietic stem cells (HSCs) towards erythroid, myeloid and lymphoid lineages. To dissect early lymphoid specification events, we generated two transgenic mouse models reporting and tracing the expression of terminal deoxynucleotidyl transferase (TdT). Surprisingly, transient induction of TdT was detected on a newly identified multipotent progenitor (MPP) subset which lacked self-renewal capacity but maintained multilineage differentiation potential. TdT induction by MPPs reflected a transcriptionally dynamic but uncommitted stage characterized by low expression of lineage-associated genes. Further, analysis using single-cell CITE-Seq indicated that multipotency is associated with expression of Endothelial Cell-Selective Adhesion Molecule (ESAM). Developmental progression along all lineages is defined by downregulation of ESAM and by stable TdT expression within the lymphoid trajectory. Collectively, we propose a new developmental hierarchy of early hematopoietic progenitors for which we provide their transcriptional profile as well as their phenotypic and functional properties at single cell resolution. Supported by NIH intramural funding