Despite a growing body of research, Speaking Anxiety (SA) reduction has been a prominent issue in Second/Foreign Language (S/FL) learning, especially among undergraduate students. The complexity and variety of features of Speaking Anxiety Interventions (SAI) make the synthesis and application of their findings in practice challenging. This study systematically reviews the existing evidence on SAI between January 2015 and mid-June 2021 to summarize and clarify the field's current state and offer directions for future research in the context of undergraduate learners. Seven established inclusion criteria were used to select studies. The study identified 2280 potentially eligible studies through Scopus, WOS, and Science Direct, 16 of which were eventually included. The studies applied a range of methodological designs and different types of interventions with various durations. This systematic review resulted in two main categories of SAI, namely direct and indirect, according to the mechanism used to intervene with SA. In addition to exploring innovative methods to promote effective SAI, future research should examine the cause of SA and learners' speaking English proficiency levels before selecting or applying any SA reduction approach that may significantly impact the success or failure of SAI.