Successful early mathematical development is vital to children's later education, employment, and wellbeing outcomes. However, established measurement tools are infrequently used to (i) assess children's mathematical skills and (ii) identify children with or at-risk of mathematical learning difficulties. In response, this pre-registered systematic review aimed to provide an overview of measurement tools that have been evaluated for their psychometric properties for measuring the mathematical skills of children aged 0-8 years. The reliability and validity evidence reported for the identified measurement tools were then synthesised, including in relation to common acceptability thresholds. Overall, 41 mathematical assessments and 25 screeners were identified. Our study revealed five main findings. Firstly, most measurement tools were categorised as child-direct measures delivered individually with a trained assessor in a paper-based format. Secondly, the majority of the identified measurement tools have not been evaluated for aspects of reliability and validity most relevant to education measures, and only 15 measurement tools met the common acceptability thresholds for more than two areas of psychometric evidence. Thirdly, only four screeners demonstrated an acceptable ability to distinguish between typically developing children and those with or at-risk of mathematical learning difficulties. Fourthly, only one mathematical assessment and one screener met the common acceptability threshold for predictive validity. Finally, only 11 mathematical assessments and one screener were found to concurrently align with other validated measurement tools. Building on this current evidence and improving measurement quality is vital for raising methodological standards in mathematical learning and development research.