Objective The aim of this study was to test dietary restriction (DR) as an intervention to alleviate senescence-associated functional defects in hematopoietic stem cells (HSCs). Materials and methods BALB/cByJ (BALB) mice were fed ad libitum (AL) or were diet restricted (DR) to 75% of the AL food intake after 1 month of age. Peripheral blood and bone marrow cell compositions were compared in 3- and 25-month-old AL (AL-3, AL-25) mice and in 25-month-old DR (DR-25) mice using fluorescence-activated cell staining. Relative HSC functions in vivo were compared using competitive repopulation, and were also tested in 6-month-old BALB mice to measure the effects of short-term DR. Results Compared to AL-3, AL-25 blood had significantly lower levels of red blood cells and hemoglobin. AL-25 marrow contained less than half the concentration of Lin −CD34 −Sca1 +CD117 + HSCs and showed only half the in vivo functional ability of AL-3 marrow. In vivo, AL-25 HSCs failed to produce the strong correlations over time that demonstrate clonal stability during competitive repopulation. These correlations were shown in AL-3 HSCs. DR for 24 months alleviated hematopoietic deficiencies in the blood, increased concentrations of bone marrow Lin −CD34 −Sca1 +CD117 + HSCs and improved HSC functional abilities in DR-25 mice to values far greater than those in normally aged mice. Surprisingly, HSC function in 25-month-old DR mice was better than that in young adults. Degrees of recipient repopulation by HSCs from DR-25 mice also correlated well over time, demonstrating clonal stability. Short-term DR for 5 months also improved HSC function, but to a much smaller degree. Conclusions Aged BALB mice show hematopoietic and HSC senescence and clonal succession. Lifelong DR slows hematopoietic senescence and prevents HSC aging.