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, 37 mathematical assessments and 22 screeners were identified. In addressing the first aim, most measurement tools were categorised as child-direct measures delivered individually with a trained assessor in a paper-based format. In addressing the second aim, the synthesis revealed four key findings. First, the majority of the identified measurement tools have not been evaluated for all aspects of reliability and validity, and only seven measurement tools met the common acceptability thresholds for more than two areas of psychometric evidence. Second, only three screeners demonstrated an acceptable ability to distinguish between typically developing children and those with or at-risk of mathematical learning difficulties. Third, although five mathematical assessments and six screeners included evaluations of predictive validity, none met the common acceptability threshold. Finally, only eight mathematical assessments and one screener were found to align with external measurement tools. Building on this current evidence and improving measurement quality is vital for raising methodological standards in mathematical learning and development research.