Objective: This study investigated a multicomponent cognitive behavioral treatment (CBT) for hoarding based on a model proposed by Frost and colleagues and manualized in Steketee and Frost (2007). Method: Participants with clinically significant hoarding were recruited from the community and a university-based anxiety clinic. Of the 46 patients randomly assigned to CBT or waitlist (WL), 40 completed the 12-week assessment and 36 completed 26 sessions. Treatment included education and case formulation, motivational interviewing, skills training for organizing and problem solving, direct exposure to nonacquiring and discarding, and cognitive therapy. Measures included the Saving Inventory-Revised (self-report), Hoarding Rating Scale-Interview, and measures of clinical global improvement. Between group repeated measures analyses using general linear modeling examined the effect of CBT versus WL on hoarding symptoms and moodstate after 12 weeks. Within group analyses examined pre-post effects for all CBT participants combined after 26 sessions. Results: After 12 weeks, CBT participants benefited significantly more than WL patients on hoarding severity and mood with moderate effect sizes. After 26 sessions of CBT, participants showed significant reductions in hoarding symptoms with large effect sizes for most measures. At session 26, 71% of patients were considered improved on therapist clinical global improvement ratings and 81% of patients rated themselves improved; 41% of completers were clinically significantly improved. Conclusions: Multicomponent CBT was effective in treating hoarding. However, treatment refusal and compliance remain a concern, and further research with independent assessors is needed to establish treatment benefits and durability of gains. Depression and Anxiety, 2010. © 2010 Wiley-Liss, Inc.