K(Lysine) Acetyltransferase 8 (KAT8, also known as MOF) is a histone 4 lysine 16 (H4K16) acetyltransferase and crucial for murine embryogenesis. Lysine acetyltransferases have been shown to regulate various stages of normal hematopoiesis. However, the function of Mof in hematopoietic stem cell (HSC) development has not yet been elucidated. We set out to study the role of MOF in general hematopoiesis by using a Vav1-cre induced conditional murine Mof knockout system, and found that MOF is critical for hematopoietic cell maintenance and HSC engraftment capacity in adult hematopoiesis. Rescue experiments with a Mof histone acetyltransferase domain mutant illustrated the requirement for Mof acetyltransferase activity in the clonogenic capacity of HSCs and progenitors. In stark contrast, fetal steady-state hematopoiesis at embryonic day 14.5 was not affected by homozygous Mof deletion despite dramatic loss of global H4K16ac. Hematopoietic defects start manifesting in late gestation at E17.5. The discovery that Mof and its H4K16 acetyltransferase activity are required for adult, but not early and mid gestational hematopoiesis, supports the notion that multiple chromatin regulators may be crucial for hematopoiesis at varying stages of development. Mof is therefore a developmental-stage-specific chromatin regulator found to be essential for adult, but not early fetal hematopoiesis.