Recent studies have suggested that CD300A was an oncogene in acute myeloid leukemia (AML) development. However, the clinical relevance and biological insight into CD300A expression in AML are still not well understood. The present study aimed to examine the expression characteristics of CD300A in AML and confirmed its clinical significance for AML. Quantification of the CD300A transcript was performed in 119 AML patients by real-time quantitative PCR in bone marrow blasts. The predictive significance of CD300A expression on the clinical outcomes of AML was assessed using overall survival (OS) and relapse-free survival (RFS). The published Cancer Genome Atlas (TCGA) data were used as an external validation for survival analysis and pathway analyses. In comparison with monocytes from healthy peripheral blood cells, the expression levels of CD300A in AML cells were higher. Patients in the intermediate and adverse risk categories by WHO criteria (2018) had higher CD300A expression levels than those in the favorable risk category (p < 0.001). AML patients with high expression of CD300A had a higher early death rate (p = 0.029), lower complete remission rate (p = 0.042), higher death rate (p < 0.001) and relapse rate (p = 0.002), and shorter OS (p < 0.0001) and RFS (p < 0.0001). Through multivariable analysis, high CD300A expression in AML was also an independent poor prognostic factor. The CAMP and CGMP-PKG signaling pathways may be stimulated by increased CD300A expression levels, which may be important for the development of AML. The expression levels of CD300A were associated with risk stratification and the clinical relevance of AML. High CD300A expression may act as an independent adverse prognostic factor for OS and RFS in AML.