Disclosed are histone deacetylase (HDAC) inhibitors, or combinations comprising an HDAC inhibitor and a Bruton' s tyrosine kinase (BTK) inhibitor, for the treatment of chronic lymphocytic leukemia in a subject in need thereof. Also provided herein are methods for treating chronic lymphocytic leukemia in a subject in need thereof comprising administering to the subject a therapeutically effective amount of an HDAC inhibitor, or a combination comprising an HDAC inhibitor and a BTK inhibitor. Other related methods are disclosed.