This article presents the Synthesis Methods and Reporting Tool (SMART), a guide on methodological and reporting practices for all types of research synthesis (RS) in applied linguistics. Informed by RS checklists and tools in other disciplines, SMART is developed based on published RSs and methodological publications on RS in applied linguistics. To ensure SMART is field-specific, a group of RS specialists in applied linguistics provided input and feedback. SMART is underpinned by four principles (STAR): systematicity, transparency, accessibility, and reflexivity, and comprising three key stages (preparation, method, and reporting); it aims to cover all procedures and practices that need to be considered before, during, and after conducting an RS. A unique feature of SMART is the inclusion of baseline and preferred practices: “baseline practices” refer to minimum requirements that an RS needs to meet while “preferred practices” provide suggestions that researchers are encouraged to implement. The introduction of SMART provides the applied linguistics community, especially those new to RS, with an easy-to-use tool to guide RS methodologies. While the intention is not to replace other RS tools, SMART is developed to be responsive to the development, standard and characteristics of RS in applied linguistics.