Results from the Trends in International Mathematics and Science Study (TIMSS) assessments have shown that students in Korea displayed high levels of science achievement. In order to understand those achievement outcomes, a number of studies have examined science teaching in Korea and explored the effects of teaching practices on student achievement and beliefs about science. The purpose of this study was to examine the relationship between confidence in science and chemistry achievement test scores for eighth-grade students in Korea who participated in the TIMSS 2015 assessment. Students included in this study were from the TIMSS 2015 eighth-grade (Population 2) sample from Korea. Several significant findings were noted. Students who expressed positive appraisals of their abilities in science were more likely to show higher levels of chemistry achievement. Conversely, students in Korea who made negative comparisons of themselves to other students tended to show lower chemistry achievement test scores.