Background: Depression is an important health issue amongst older adults. Internet-delivered cognitive behaviour therapy (iCBT) may help to reduce barriers and improve access to treatment, but few studies have examined its use with older adults. The present study evaluated the efficacy, acceptability and feasibility of a brief iCBT program, the Managing Your Mood Program, to treat depression amongst adults aged 60 years and older. Method: Using an open trial design, 20 participants with elevated symptoms of depression (Patient Health Questionnaire 9-item (PHQ-9) total scores > 10) received access to five educational lessons and homework summaries, additional resources, a moderated discussion forum and weekly telephone or email contact from a clinical psychologist. Eighty percent of the sample met diagnostic criteria for a major depressive episode at pre-treatment. Results: Completion rates and response rates were high, with 16/20 participants completing the five lessons within the 8 weeks, and post-treatment and 3-month follow-up data being collected from 17/20 participants. Participants improved significantly on the PHQ-9 and Geriatric Depression Scale (GDS), with large within-group effect sizes (Cohens d) at follow-up of 1.41 and 2.04, respectively. The clinician spent a mean time of 73.75 minutes (SD = 36.10 minutes) contacting participants within the trial and the program was rated as highly acceptable by participants. Conclusions: The results are encouraging and support the potential value of iCBT in the treatment of depressive symptoms amongst older adults.