This phase I trial studies the side effects and best dose of lenalidomide when given together with ibrutinib in treating patients with chronic lymphocytic leukemia or small lymphocytic lymphoma that has returned after a period of improvement or does not respond to treatment. Biological therapies, such as lenalidomide, may stimulate the immune system in different ways and stop cancer cells from growing. Ibrutinib may stop the growth of cancer cells by blocking some of the enzymes needed for cell growth. Giving lenalidomide together with ibrutinib may work better in treating chronic lymphocytic leukemia or small lymphocytic lymphoma.