Rationale Cerebral small vessel disease (CSVD) is responsible for 25% of ischaemic strokes and 45% of dementia cases. Currently, therapies targeting individual mechanisms have not shown significant efficacy. As CSVD involves multiple pathophysiological mechanisms, Cerebralcare pills, a traditional Chinese medicine with multiple pharmacological mechanisms, may be effective in treating cognitive dysfunction in CSVD.Aims The objective of this study was to assess the efficacy of Cerebralcare pills in improving cognitive dysfunction (measured by Montreal Cognitive Assessment (MoCA)) in patients with CSVD.Sample size estimates A sample size of 114 patients with CSVD (57 in each group) will allow 2.74 points (with an SE of 0.56 points) difference between two groups on the MoCA score with 5% significance, 80% power and assuming a 10% dropout rate.Methods and design This is a randomised double-blind, multicentre, placebo-controlled trial involving individuals with mild cognitive impairment (MoCA score ranging from 16 to 24) associated with CSVD. CSVD was defined by the presence of white matter hyperintensities consistent with lacunar infarcts or the presence of more than two vascular risk factors. Participants were randomised 1:1 to orally take 5 g of Cerebralcare pills or placebo twice a day for 6 months.Study outcomes The primary outcome measure is the change in MoCA score at 6 months. Secondary outcome measures include the assessment of clinical manifestations, cognitive performance, conventional MRI markers, blood-brain barrier permeability and proteomics over a follow-up period of 6 months and 12 months.Discussion The objective of this trial is to evaluate the efficacy of Cerebralcare pills in improving cognitive dysfunction associated with CSVD. Additionally, the trial aims to provide insights into the pathological processes involved in this condition.Trial registration number NCT05578521.