OBJECTIVES: To assess whether older persons with osteoarthritis (OA) pain and insomnia receiving cognitive-behavioral therapy for pain and insomnia (CBT-PI), a cognitive-behavioral pain coping skills intervention (CBT-P), and an education-only control (EOC) differed in sleep and pain outcomes. DESIGN: Double-blind, cluster-randomized controlled trial with 9-month follow-up. SETTING: Group Health and University of Washington, 2009 to 2011. PARTICIPANTS: Three hundred sixty-seven older adults with OA pain and insomnia. INTERVENTIONS: Six weekly group sessions of CBT-PI, CBT-P, or EOC delivered in participants' primary care clinics. MEASUREMENTS: Primary outcomes were insomnia severity and pain severity. Secondary outcomes were actigraphically measured sleep efficiency and arthritis symptoms. RESULTS: CBT-PI reduced insomnia severity (score range 0-28) more than EOC (adjusted mean difference = -1.89, 95% confidence interval = -2.83 to -0.96; P < .001) and CBT-P (adjusted mean difference = -2.03, 95% CI = -3.01 to -1.04; P < .001) and improved sleep efficiency (score range 0-100) more than EOC (adjusted mean difference = 2.64, 95% CI = 0.44-4.84; P = .02). CBT-P did not improve insomnia severity more than EOC, but improved sleep efficiency (adjusted mean difference = 2.91, 95% CI = 0.85-4.97; P = .006). Pain severity and arthritis symptoms did not differ between the three arms. A planned analysis in participants with severe baseline pain revealed similar results. CONCLUSION: Over 9 months, CBT of insomnia was effective for older adults with OA pain and insomnia. The addition of CBT for insomnia to CBT for pain alone improved outcomes.