Background: WHO's iSupport Lite comprises six messages designed to reduce stress and improve the mental health and wellbeing of carers of people with dementia. We culturally adapted iSupport Lite into Draw-Care, a multilingual digital intervention . We evaluated its effectiveness in reducing carer burden and improving mood and quality of life. Methods: We conducted a single-blind, parallel, national community trial with multilingual adult carers. The intervention was delivered online between 1/08/2023 and 8/11/2024, with follow-up at 6 and 12 weeks. The primary outcome was carer burden measured using the ZBI. Secondary outcomes included mood and quality of life measures, and a productivity and activity impairment measure. A realist evaluation applied the Context–Mechanism–Outcome heuristic. Results: Of 116 carers who consented, 93 were included in the analyses, and 37 participated in the realist evaluation. Participants’ mean age was 54.8 years (SD 13.3); and 77.4% were women. We observed significantly higher mean CarerQoL-VAS scores across 6 and 12 weeks in the intervention group compared with controls (mean difference = 0.75; 95% CI 0.25–1.24; p = 0.003). There were no other statistically significant differences. Post hoc analyses among 42 carers reporting work-care role conflict showed significant reductions in ZBI scores at 6 weeks (−7.59; 95% CI −12.97 to −2.22) and 12 weeks (−6.85; 95% CI −12.21 to −1.49). The realist evaluation showed that Draw Care activated cognitive reframing, reduced stigma, validated help-seeking, and strengthened care relationships and mood. Conclusion: Draw Care can improve quality of life overall, and mood and carer burden among carers experiencing work-care role conflict.