CONTEXT: In older people, depressive symptoms are common, psychological adjustment to aging is complex, and associated chronic physical illness limits the use of antidepressants. Despite this, older people are rarely offered psychological interventions, and only 3 randomized controlled trials of individual cognitive behavioral therapy (CBT) in a primary care setting have been published. OBJECTIVE: To determine the clinical effectiveness of CBT delivered in primary care for older people with depression. DESIGN: A single-blind, randomized, controlled trial with 4- and 10-month follow-up visits. PATIENTS: A total of 204 people aged 65 years or older (mean [SD] age, 74.1 [7.0] years; 79.4% female; 20.6% male) with a Geriatric Mental State diagnosis of depression were recruited from primary care. INTERVENTIONS: Treatment as usual (TAU), TAU plus a talking control (TC), or TAU plus CBT. The TC and CBT were offered over 4 months. OUTCOME MEASURES: Beck Depression Inventory-II (BDI-II) scores collected at baseline, end of therapy (4 months), and 10 months after the baseline visit. Subsidiary measures were the Beck Anxiety Inventory, Social Functioning Questionnaire, and Euroqol. Intent to treat using Generalized Estimating Equation and Compliance Average Causal Effect analyses were used. RESULTS: Eighty percent of participants were followed up. The mean number of sessions of TC or CBT was just greater than 7. Intent-to-treat analysis found improvements of -3.07 (95% confidence interval [CI], -5.73 to -0.42) and -3.65 (95% CI, -6.18 to -1.12) in BDI-II scores in favor of CBT vs TAU and TC, respectively. Compliance Average Causal Effect analysis compared CBT with TC. A significant benefit of CBT of 0.4 points (95% CI, 0.01 to 0.72) on the BDI-II per therapy session was observed. The cognitive therapy scale showed no difference for nonspecific, but significant differences for specific factors in therapy. Ratings for CBT were high (mean [SD], 54.2 [4.1]). CONCLUSION: Cognitive behavioral therapy is an effective treatment for older people with depressive disorder and appears to be associated with its specific effects. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN18271323.