Background: Demographic and epidemiological changes place an increasing reliance on informal carers. Some support programmes exist, but funding is often limited. There is a need for economic evaluation of interventions for carers to assist policymakers in prioritizing carer support. Objective: Our aim was to systematically review and critically appraise cost–utility analyses of interventions for informal carers, in order to assess the methods employed and the quality of the reporting. Methods: A systematic review of databases was conducted using MEDLINE, Embase, PsycINFO, and EconLit of items published between 1950 and February 2019. Published studies were selected if they involved a cost–utility analysis of an intervention mainly or jointly targeting informal carers. The reporting quality of economic analyses was evaluated using the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) statement. Results: An initial set of 1364 potentially relevant studies was identified. The titles and the abstracts were then screened, resulting in the identification of 62 full-text articles that warranted further assessment of their eligibility. Of these, 20 economic evaluations of informal carer interventions met the inclusion criteria. The main geographical area was the UK (n = 11). These studies were conducted in mental and/or behavioural (n = 15), cardiovascular (n = 3) or cancer (n = 2) clinical fields. These cost–utility analyses were based on randomized clinical trials (n = 16) and on observational studies (n = 4), of which only one presented a Markov model-based economic evaluation. Four of the six psychological interventions were deemed to be cost effective versus two of the four education/support interventions, and four of the nine training/support interventions. Two articles achieved a CHEERS score of 100% and nine of the economic evaluations achieved a score of 85% in terms of the CHEERS criteria for high-quality economic studies. Conclusions: Our critical review highlights the lack of cost–utility analyses of interventions to support informal carers. However, it also shows the relative prominence of good reporting practices in these analyses that other studies might be able to build on.