Purpose: Carers of stroke survivors face a range of challenging demands. There is an increasing interest in using mindfulness-based interventions (MBIs) to provide support for carers. The main aims of this study were to assess the acceptability of an online MBI for carers of stroke survivors and the feasibility of recruiting into a wait-list controlled study design. Methods: Carers of stroke survivors were recruited through charitable and voluntary organisations. Participants were randomised to the intervention (an online, four-week MBI) or waitlist control group. Primary outcomes included participant feedback and/or interview, recruitment and retention rates and reports of intervention adherence. Outcome measures assessing burden, quality of life, stress, depression, anxiety, mindfulness and coping were also administered. Results: Twenty-seven people requested or made contact regarding the study and 15 consenting participants were screened and randomised. At six weeks, attrition was 40%. Overall, 12/15 participants accessed the MBI. Five participants completed it and feedback indicated the MBI was acceptable to them. Qualitative data from one withdrawn participant identified barriers to taking part. Intervention adherence could not be reliably assessed. Group medians, interquartile ranges and individual change analyses did not indicate a clear pattern of changes on outcome measures, although evidence of improvement and deterioration were identified on some. Conclusions: Results suggest limited feasibility of extending the current methodology to a larger trial. Carers' situations may pose limitations on their ability to engage in an online MBI, although for a subset of carers, this intervention appears acceptable. Recommendations for future trials are made.