ESS2 (ess-2 splicing factor homolog, also known as DGCR14 or DGS-I) is a member of the deletion gene cluster in the 22q11.2 deletion syndrome (22q11.2DS, also known as DiGeorge syndrome or CATCH 22 syndrome). The ESS2 gene is not part of a gene family, and the coded protein has a coiled-coil structure (Es domain), which is conserved from yeast to humans. Recent studies have shown that ESS2 is involved in splicing C and C* complex, but other interactants, such as transcription factors and U1 snRNP, are also reported. Although the molecular mechanism is still under investigation, ESS2 plays a pivotal role in cell differentiation and proliferation. ESS2 knockout mice show embryonic lethal in the early stage, and recent studies show the association of ESS2 with cancer, autoimmune disease, and neurodevelopmental disorders. ESS2 can regulate mRNA splicing and transcriptional activity through interactions with other proteins, and ESS2-dependent gene expression regulation seems to be cell type-selective. In this review, we summarized the cloning history and functions of ESS2, including recent findings.