CD26/DPPIV is a dipeptidyl peptidase that cleaves and destroys a variety of substrates such as the chemokine SDF-1α, a chemokine expressed along bone marrow endothelium, which is essential for the recruitment of hematopoietic stem cells (HSCs) via binding with its receptor CXCR4 to the bone marrow. Thus, CD26 is thought to interfere with the second step, chemokine/chemokine receptor interactions, of the cellular migration paradigm. To further study the role of CD26 in the migration of HSCs, we screened several human leukemic cell lines to find a model cell line that expresses active CD26 and discovered that the pro-monocytic cell line, U937 was optimal for this purpose. U937 cells were used to optimize a variety of assays including an CD26 activity assay and transwell migration assay with and without the use of a CD26 inhibitor, Diprotin A. Then, we isolated short-term and long-term HSCs from the bone marrow of C57BL/6N mice using a combination of surface markers and a fluorescence-activated cell sorter. The expression levels of Step 2’s homing molecules were measured by FACS in both fractions of HSCs. Interestingly, we detected differences in the expression of CD26 between these two populations that may help explain the inability of long-term HSCs to migrate to the bone marrow. Thus, through the use of a CD26 inhibitor the long-term HSCS migration to the bone marrow could be enhanced, leading to a prolonged and efficient stem cell engraftment activity. Such studies are could help develop protocols to improve stem cell engraftment for patients suffering from hematological diseases such as leukemia.