Test-taking motivation (TTM) has been found to have a profound effect on low-stakes test results. From the components of TTM test-taking effort has been shown to be the strongest predictor of test performance. This article presents an overview of methods and instruments used to measure TTM and effect sizes between test-taking effort and performance found with these instruments. Altogether 104 articles were included in the qualitative synthesis based on literature search in EBSCO Discovery database. Effect sizes for the relationship between test-taking effort and performance were available in 28 studies. The average correlation between self-reported effort and performance was r = .33 and the average correlation between Response Time Effort and performance was r = .72, indicating that these two types of measures could be distinctly different. Educational level was a significant moderator of the effect sizes: the average correlation between test-taking effort and performance was stronger for university students than for school students. An overview of interventions aimed to enhance TTM and their effect is given. •The average correlation between self-reported effort and test score is r = 0.33•The average correlation between Response Time Effort and test score is r = 0.72•Educational level moderates the relationship between self-reported effort and test performance.