Early B cell factor 1 (EBF1) is one of the key transcription factors required for orchestrating B-cell lineage development. Although studies have shown that Ebf1 haploinsufficiency is involved in the development of leukemia, no study has been conducted that characterizes the global effect of Ebf1 heterozygosity on the proteome of pro-B lymphocytes. Here, we employ both DIA (Data Independent Acquisition) and shotgun DDA (Data Dependent Acquisition) workflows for profiling proteins that are differently expressed between Ebf1+/+ and Ebf1+/- cells. Both DDA and DIA were able to reveal the downregulation of the EBF1 transcription factor in Ebf1+/- pro-B lymphocytes. Further examination of differentially expressed proteins by DIA revealed that, similar to EBF1, the expression of other B-cell lineage regulators, such as TCF3 and Pax5, is also down-regulated in Ebf1 heterozygous cells. Functional DIA analysis of differentially expressed proteins showed that EBF1 heterozygosity resulted in the deregulation of at least 8 transcription factors involved in lymphopoiesis, and to the deregulation of key proteins playing crucial roles in survival, development and differentiation of pro-B lymphocytes.