Objectives To investigate the effects on carer well‐being of carer involvement in cognition‐based interventions (CBIs) for people with dementia. Methods A review and meta‐analysis were performed. We searched electronic databases for randomised controlled trials (RCTs). Two reviewers worked independently to select trials, extract data and assess the risk of bias. Results A total of 4737 studies was identified. Eight RCTs met the inclusion criteria. Only seven studies with 803 dyads of people with dementia and carers were included in the meta‐analysis. Evidence indicated that carer involvement in CBIs for people with dementia had a beneficial effect on carers' quality of life with effect size Hedges' g = 0.22; 95% confidence interval of 0.02 to 0.42, z = 2.19 and p = 0.03. Carers' depression levels were reduced in the intervention group with effect size Hedges' g = 0.17; 95% confidence interval of 0.02 to 0.32, z = 2.19 and p = 0.03. No significant differences were observed in levels of anxiety symptoms, caregiving relationship and carer burden in the intervention group compared to those in the control group. Conclusion Because CBIs are designed to deliver benefit for people with dementia, the collateral benefits for carers have potential implications for the importance of CBIs in service delivery and may contribute to cost effectiveness. However, there remains a lack of quality of research in this area. Particularly, in some outcomes, there was a lack of consistency of results, so the findings should be interpreted with caution. Future studies of the impact of CBIs on carers with larger samples and high‐quality RCTs are warranted. Copyright © 2017 John Wiley & Sons, Ltd.