Objective The purpose of this review is to evaluate the tools used to measure the financial value of libraries in a clinical setting. Methods Searches were carried out on ten databases for the years 2003—2013, with a final search before completion to identify any recent papers. Results Eleven papers met the final inclusion criteria. There was no evidence of a single ‘best practice’, and many metrics used to measure financial impact of clinical libraries were developed on an ad hoc basis locally. The most common measures of financial impact were value of time saved, value of resource collection against cost of alternative sources, cost avoidance and revenue generated through assistance on grant submissions. Few papers provided an insight into the longer term impact on the library service resulting from submitting return on investment (ROI) or other financial impact statements. Conclusions There are limited examples of metrics which clinical libraries can use to measure explicit financial impact. The methods highlighted in this literature review are generally implicit in the measures used and lack robustness. There is a need for future research to develop standardised, validated tools that clinical libraries can use to demonstrate their financial impact.