Obesity, resulting from excessive adipocyte accumulation, is a primary risk for various diseases. Although its impact on hematopoietic stem cell (HSC) function has been reported, its effects on HSC differentiation remain controversial. O-GlcNAc transferase (OGT), which catalyzes the attachment of N-acetylglucosamine to serine and threonine residues in proteins, acts as a metabolic sensor capable of regulating diverse physiological processes. This study demonstrates that obesity is associated with higher peripheral monocyte levels. Adipocyte OGT is crucial for monocyte development in high-fat diet (HFD)-induced obesity, promoting an increase in peripheral blood monocytes through transcriptional activation of nonesterified fatty acids (NEFA), a critical energy substrate. Loss of adipocyte OGT decreases serum NEFA levels, reduces white adipose tissue, and inhibits HSC differentiation into monocytes in HFD-induced obesity. Mechanistically, the regulated effect of adipocyte OGT on monocyte development may be mediated by NEFA-cluster of differentiation 36/fatty acid binding protein 4 (CD36/FABP4) pathway in HSCs in HFD-induced obesity. These findings establish the critical role of adipocyte OGT in hematopoietic homeostasis and monocyte development.