Background Post-stroke cognitive impairment (PSCI) affects approximately 40% of stroke survivors within one year, yet cognitive rehabilitation is not routinely integrated into post-stroke care. This protocol outlines a pilot randomised controlled trial (RCT) to assess the feasibility, acceptability, and preliminary effectiveness of a structured cognitive rehabilitation programme, StrokeCog-R , for PSCI. A nested Study Within A Trial (SWAT) will evaluate the impact of follow-up communication methods on participant retention. Methods Sixty-four stroke survivors will be recruited and randomly assigned to either a StrokeCog-R intervention ( n = 32) or control (usual care; n = 32) group. StrokeCog-R is a five-week, group-based cognitive rehabilitation/psychoeducation programme targeting executive function, memory, and attention, delivered by a clinical neuropsychologist. Primary outcomes include recruitment, retention, intervention acceptability, and cognition. Cognitive function will be assessed using the National Institute for Neurological Disorders and Stroke (NINDS) battery at baseline (six weeks post-stroke), immediately post-intervention/control period, and at a four-month follow-up. Secondary outcomes include self-efficacy, functional ability, mood, as well as carer-rated cognitive and behavioural changes and carer wellbeing. The SWAT will examine whether additional text messages during the follow-up period improve retention at the four-month assessment compared to telephone calls alone. Recruitment and retention rates will be reported with 95% confidence intervals. Effect size estimates from pre- to post-intervention changes in cognition will inform sample size calculations for a future definitive trial. Qualitative data will be analysed using a reflexive thematic approach, guided by the Consolidated Framework for Implementation Research (CFIR). Results This pilot RCT will assess the feasibility of conducting a full-scale definitive RCT, including recruitment and retention rates, and preliminary outcome trends. SWAT findings will guide future retention strategies. Conclusions Findings will inform the design of a larger RCT and, if feasible, support the potential integration of cognitive rehabilitation into routine post-stroke care to improve long-term cognitive outcomes.