Inclusion Criteria:

          -  Understand and voluntarily sign an informed consent form

          -  Able to adhere to the study visit schedule and other protocol requirements including
             willing to provide blood, baseline bone marrow aspirate, and control deoxyribonucleic
             acid (DNA) samples for correlative research purposes

          -  Diagnosis of B-cell chronic lymphocytic leukemia (B-CLL), confirmed by flow cytometry
             and as per the criteria outlined by the IWCLL/Hallek December 2008

          -  Prior frontline therapy for B-CLL must have been discontinued >= 56 days but =< 365
             days prior to registration; NOTE: Patients on supportive care therapy due to use of
             specific induction regimen such as antibiotics may continue on those treatments at the
             discretion of the treating physician

          -  Patient must have completed a frontline induction therapy (minimum of 2 treatment
             cycles); NOTE: Standard therapies/therapeutic agents are defined as those listed in
             the National Comprehensive Cancer Network (NCCN) guidelines for treatment of CLL;
             also, patients who received induction regimen as part of a clinical trial and is not
             necessarily mentioned in the NCCN guidelines, will also be eligible as long as the
             patient has completed at least 2 treatment cycles of induction regimen, achieved a
             clinical response (PR or CR) and is able to meet all other criteria for the study;
             however, patients who have previously received ibrutinib or have been randomized to
             ibrutinib containing arms in a clinical trial will not be eligible for this study

          -  Patients must have a sustained clinical response (PR, nodular PR [nPR], complete
             clinical response [CCR], CR with incomplete marrow recovery [CRi], CR) with documented
             residual disease (>= 1 CLL cell per 10,000 leukocytes or >= 0.01% MRD) either in the
             blood, bone marrow or a lymph node >= 3.5 cm by any available techniques

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1 or 2 at
             registration

          -  Absolute neutrophil count >= 1000/mm^3

          -  Platelet count >= 30,000/mm^3

          -  Serum creatinine =< 1.5 x upper limit of normal (ULN)

          -  Total bilirubin =< 1.5 mg/dL or direct bilirubin =< 1.0 mg/dL for patients with
             Gilbert's syndrome

          -  Serum glutamic oxaloacetic transaminase (SGOT) (aspartate aminotransferase [AST]) and
             serum glutamate pyruvate transaminase (SGPT) (alanine aminotransferase [ALT]) =< 3.5 x
             ULN

          -  Negative pregnancy test done =< 7 days prior to registration, for women of
             childbearing potential only

        Exclusion Criteria:

          -  Any serious medical condition, laboratory abnormality, or psychiatric illness that
             would prevent the subject from signing the informed consent form

          -  Since this study involves an investigational agent whose genotoxic, mutagenic and
             teratogenic effects on the developing fetus and newborn are unknown, any of the
             following will deem the subject ineligible for the study:

               -  Pregnant women

               -  Nursing women

               -  Men or women of childbearing potential who are unwilling to employ adequate
                  contraception

          -  Any condition, including the presence of laboratory abnormalities, which places the
             subject at unacceptable risk if he/she were to participate in the study or confounds
             the ability to interpret data from the study

          -  Use of any other experimental drug or therapy =< 28 days prior to registration on this
             study; NOTE: Patients on low dose prednisone (=< 10 mg) for treatment of conditions
             other than CLL are eligible

          -  Patients who have received more than 1 prior therapy; NOTE: Prior therapy is defined
             as any single agent or combination regimen that is included as treatment for
             symptomatic CLL; treatment(s) given prior to the symptomatic phase of the disease
             (preventive strategy) will not be considered as prior induction therapy; for the
             purpose of a particular therapy/regimen to be counted towards the number of prior
             treatments a patient must have received at least 2 cycles of the induction regimen
             e.g., a patient who change their treatment regimen after only 1 cycle (due to toxicity
             or any other reason) will not be considered to have "2" prior therapies

          -  Patients who have progressive disease or relapse (as defined by the IWCLL criteria) at
             or any time before registration on this study

          -  Patients with history of any other cancer (except non-melanoma skin cancer or
             carcinoma in-situ of the cervix, unless in complete remission and off therapy for that
             disease for > 3 years)

          -  Patients who are already MRD- (both in the blood and the bone marrow) after frontline
             therapy and have lymph nodes < 3.5 cm

          -  Concomitant use of warfarin or other vitamin K antagonists

          -  Requires treatment with a strong cytochrome P450 modulators (cytochrome P450, family
             3, subfamily A [CYP3A] inhibitor and/or CYP3A inducers)

          -  Currently active, clinically significant hepatic impairment Child-Pugh class B or C
             according to the Child Pugh classification

          -  Major surgery =< 4 weeks prior to registration

          -  Patients who have active infectious hepatitis

          -  Patients with other diseases that in the opinion of the treating physician pose a
             higher risk for treatment with ibrutinib therapy including active human
             immunodeficiency virus (HIV) infection and bleeding disorders