The Plk1‐interacting checkpoint helicase (PICH) protein localizes to ultrafine anaphase DNA bridges in mitosis along with a complex of DNA repair proteins. Previous studies show PICH deficiency‐induced embryonic lethality in mice. However, the function of PICH that is required to suppress embryonic lethality in PICH‐deficient mammals remains to be determined. Previous clinical studies suggest a link between PICH deficiency and the onset of acquired aplastic anemia. Here, using Pich knock‐out (KO) mouse models, the authors provide evidence for a mechanistic link between PICH deficiency and defective hematopoiesis. Fetal livers from Pich‐KO embryos exhibit a significantly elevated number of hematopoietic stem cells (HSCs); however, these HSCs display a higher level of apoptosis and a much‐reduced ability to reconstitute a functional hematopoietic system when transplanted into lethally irradiated recipients. Moreover, these HSCs show an elevated cytoplasmic dsDNA expression and an activation of the cGAS‐STING pathway, resulting in excessive production of type I interferons (IFN). Importantly, deletion of Ifnar1 or cGAS reverses the defective hematopoiesis. The authors conclude that loss of PICH results in defective hematopoiesis via cGAS‐STING‐mediated type I IFN production.