Hematopoietic stem cells (HSCs) are predominantly in a quiescent state, thereby avoiding depletion due to various stresses. However, quiescent HSCs are vulnerable to mutagenesis due to low-fidelity DNA repair. The mechanism by which HSCs avoid mutation accumulation remains to be elucidated. HSCs are normally resistant to apoptosis because of their abundant expressions of pro-survival Bcl-2 family genes. In contrast, p53 is activated in HSCs in response to DNA damage. We have recently shown that pro-apoptotic Bcl-2 signals are activated through p53 preferentially in HSCs with damaged DNA. Aspp1, an apoptosis-stimulating protein of p53, is highly expressed in HSCs and coordinates with p53 to maintain the genomic soundness of the HSC pool. In this review, we will summarize apoptosis regulation and the roles of p53 in HSCs, and introduce our findings showing coordinated regulations of HSC self-renewal, DNA damage tolerance and hematological malignancies by Aspp1 and p53.