TIMSS routinely presents very powerful evidence showing that students with more positive motivation toward learning science have substantially higher achievement. The results from TIMSS 2011 are consistent with previous assessments. This study explored the predictive effects of motivation toward learning science on science achievement among Malaysian and Singaporean eighth graders who participated in the TIMSS 2011. In this study, students' interest in and liking of learning science, students' understanding about the importance and the usefulness of the science subject, and students' self-confidence or self-concept in their ability to learn science were measured. Secondary data of the study were obtained from 5,733 Malaysian students and 5,927 Singaporean students who participated in the TIMSS 2011. The results of the present study indicated that eighth-graders' liking and valuing of learning science were positively associated with Malaysian and Singaporean Grade 8 students' science achievement.