Patients receive obinutuzumab intravenously (IV) over 30 minutes on days 1, 8, 15 (course 1) and day 1 (courses 2-6). Patients also receive ibrutinib orally (PO) once daily (QD) beginning on day 1 (course 1). Treatment repeats every 28 days for 6 courses in the absence of disease progression or unacceptable toxicity. Patients achieving partial response (PR) continue to receive obinutuzumab IV every 2 months and ibrutinib PO QD for up to 2 years in the absence of disease progression or unacceptable toxicity.