The present disclosure provides human monoclonal antibodies that bind specifically to CXCR4 with high affinity. This disclosure also provides a method for treating a subject afflicted with a CXCR4-expressing cancer, in particular a hematological malignancy such as multiple myeloma, acute myeloid leukemia, or non-Hodgkins lymphoma, comprising administering to the subject a therapeutically effective amount of a pharmaceutical composition comprising an anti-CXCR4 antibody of the disclosure. The disclosure further provides a kit for treating a cancer in a subject comprising a dose of an anti-CXCR4 antibody and instructions for using the anti-CXCR4 antibody in the therapeutic methods of the disclosure.