Acquiring strong math skills is essential in science, technology, engineering and mathematics (STEM) education. One important element to foster strong math skills is that students enjoy learning math early on during elementary school years. The control-value theory of achievement emotions (Pekrun, 2006) has been widely used to examine how specific emotions mediate the relationship between cognitive appraisals (i.e., perceived control and value) and math achievement (e.g., Putwain et al., 2018a). However, there has not been a comprehensive study examining the mediating roles of the two commonly experienced emotions—enjoyment and boredom—on international math performance. In this study, Trends in International Mathematics and Science Study (TIMSS) 2015 data is used to evaluate how enjoyment and boredom mediate the influence of cognitive appraisals on math performance in 53 education systems. Specifically, boredom significantly mediates the paths in 25 systems (47%). In general, enjoyment negatively mediates the paths which was an unexpected finding; however, 21 out of the 53 systems (40%) yield expected positive results. Our results therefore advance our understanding regarding how enjoyment and boredom relate to math success. In particular, when the mediating effects are contradictory to our hypothesis (e.g., in Korea and Turkey), these unexpected findings may indicate a cultural difference on what emotions are important to be felt in relation to academic success.