MiR-451 plays a tumor suppressive role in a variety of cancers. However, the function of miR-451 in acute myeloid leukemia (AML) has not been fully understood. Herein, we focused on the effect of miR-451 in pediatric AML and its regulatory mechanism. MiR-451 and high mobility group box 1 (HMGB1) levels were tested in bone marrow of pediatric AML patients and healthy controls, and in AML cells and HS-5 cells by qRT-PCR and Western blot analysis. HL-60 and THP-1 cells were treated with miR-451 mimics, pcDNA-HMGB1, and corresponding controls. The changes in apoptosis and autophagy were evaluated in miR-451 overexpressed AML cells with MTT and flow cytometry. The interaction between miR-451 and HMGB1 was determined by dual-luciferase reporter assay, qRT-PCR, and Western blot. After cells were co-transfected with pcDNA-HMGB1 and pc-DNA-ctrl, we investigated apoptosis and autophagy in miR-451 overexpressed cells perturbed by exogenous HMGB1 through MTT, flow cytometry, and Western blot. miR-451's role in drug sensitivity was further measured. Pediatric AML bone marrow and cell lines presented low expression of miR-451 coupled with high expression of HMGB1. HMGB1 was determined to be a functional target of miR-451. MiR-451 overexpression remarkably enhanced apoptosis and reduced autophagy in both AML cell lines, which was reversed by pcDNA-HMGB1 transfection. Additionally, exogenous miR-451 significantly enhanced the sensitivity of HL-60 cells to the chemotherapy drug As2O3. MiR-451 exerted a tumor suppressive effect in enhancing cell death and reducing autophagy of AML cells by targeting HMGB1. MiR-451 might be considered a candidate target for treating pediatric AML.