AbstractBackgroundiSupport is an online knowledge and skills training program developed by the World Health Organization to prevent and/or minimize caregiving‐associated health problems. iSupport was culturally adapted to Portugal.MethodA mixed‐methods two arm RCT was carried. Participants were recruited through the Alzheimer’s Association. Inclusion criteria are being a non‐paid caregiver; for at least six months; experiencing a clinically relevant level of burden (≥ 21 on ZBI) or depression or anxiety symptoms (≥ 8 on HADS). Eligible participants were randomized to either iSupport‐Portugal or the control arm (e‐book). Repeated measurements were collected at baseline, three (T1) and six months after baseline. Semi‐structured interviews were conducted. Usage data until T1 was extracted from iSupport’s platform. A content analysis was performed for interview data.ResultsForty‐two participants were allocated to the intervention (n=21) and control (n=21) arms. Caregivers in the intervention arm are mostly female (81%), middle‐aged (M 49 years) and highly educated (M 15.8 years of schooling). Most (81%) are children of the person with dementia, provide long‐term (Mdn 3 years) and intensive care (Mdn 29 hrs/week). Scores on ZBI (Mdn 38) and HADS‐anxiety (Mdn 12) suggest moderate to high levels of burden and anxiety. Positive attitudes towards online psychoeducation were revealed (Mdn 24 on OPI‐BAS scale). Twelve caregivers were interviewed, including dropouts. At T1, 85.7% of participants have used the program; 38.9% discontinued its use within two weeks, 66.7% within ten. On average, iSupport was accessed 8 times and 12.5 lessons were visited (in 23). One‐time‐only visitors printed the lessons (n=2); offline use is possible. Lessons on communication and shared decision making were the most visited (>90%). The qualitative data informs on the motivations and deterrents to use iSupport, usage styles, and perceived results.ConclusionA moderate acceptability of iSupport‐Portugal is suggested and might be improved with minor content and interface adjustments. Despite heterogeneous usage patterns, iSupport was mostly used intensively and during a few weeks. Conducting a re‐assessment (T1) earlier might be adequate. When nationally releasing iSupport, research on usage data must consider potential biases from unknown offline use. This pilot may inform improvements on iSupport country‐specific versions.