<p>Since the mathematics curriculum reform movement of the 1990s, mathematics teachers have been urged to adopt new instructional approaches and assessment strategies designed to help enhance students’ mathematical understanding and higher-level thinking skills. Numerous initiatives have introduced various classroom tasks—such as cognitively demanding tasks, rich tasks, problem-posing activities, and mathematical modelling—along with pedagogical approaches like inquiry-based learning, to promote students’ meaningful engagement with mathematics. Mathematics education researchers have consistently emphasized the critical role of assessment in supporting the successful implementation of mathematics curriculum reforms aimed at promoting higher-level mathematical thinking skills in students. This paper provides an overview of the research focus on the assessment of higher-level mathematical thinking skills based on a scoping review of 35 empirical studies published between 2018 and 2023. The findings indicate that a wide variety of assessment tasks, tools, and strategies have been developed and used to measure and foster students’ higher-level mathematical thinking. An increasing number of studies explored the use of digital tools and mathematical modelling tasks. Additionally, preservice teachers have been deliberately prepared to use cognitively rich assessment tasks to elicit and notice students’ mathematical thinking. The scoping review serves as the basis for a systematic review of the mathematics education and assessment literature that spans a longer period.</p>