Objective: There is a need, in the absence of formal services, to design interventions aimed at improving the lives of people with dementia and their families. This study tested the effectiveness of the 10/66 caregiver intervention among people with dementia and their caregivers in Lima, Peru. Method: Design/participants: a randomized controlled trial was performed involving 58 caregivers of people with dementia that received the intervention in the beginning of the trial (n = 29) or six months later (n = 29). The intervention consisted of three modules: 1) assessment (one session); 2) basic education about dementia (two sessions); and 3) training regarding specific problem behaviors (two sessions). Main outcome measures: Caregivers and patients with dementia were assessed at baseline and after six months. For caregivers, the measures included strain (Zarit Burden Interview), psychological distress (SRQ-20), and quality of life (WHOQOL-BREF). Dementia patients completed scales assessing behavioral and psychological symptoms (NPI-Q) and quality of life (DEMQOL). Results: Caregivers in the intervention group reported significantly decreased strain measures six months after the intervention compared to controls. No group differences were found in respect to the caregivers' psychological distress and to quality of life in both caregivers and patients. Conclusion: The 10/66 intervention seems to be as effective as similar interventions used in more developed countries.