The transcription factor CCAAT enhancer binding protein α (C/EBPα) is a master regulator in granulopoiesis and is frequently disrupted in acute myeloid leukemia (AML). We have previously shown that C/EBPα exerts its effects by regulating microRNAs (miRs) such as miR-223 and miR-34a. Here, we confirm miR-30c as a novel important target of C/EBPα during granulopoiesis. Thus, wild-type C/EBPα-p42 directly upregulates miR-30c expression, whereas C/EBPα-p30, found in AML, does not. miR-30c is downregulated in AML, especially in normal karyotype AML patients with CEBPA mutations. An induced C/EBPα knockout in mice leads to a significant downregulation of miR-30c expression in bone marrow cells. We identified NOTCH1 as a direct target of miR-30c. Finally, a block of miR-30c prevents C/EBPα-induced downregulation of Notch1 protein and leads to a reduced CD11b expression in myeloid differentiation. Our study presents the first evidence that C/EBPα, miR-30c, and Notch1 together play a critical role in granulocytic differentiation and AML, and particularly in AML with CEBPA mutations. These data reveal the importance of deregulated miRNA expression in leukemia and may provide novel biomarkers and therapeutic targets in AML.