The purpose of this study was to investigate the effect of grade level and gender on elementary school students' motivation towards science learning. A total of 2231 sixth and eight grade students participated in the study. Data were collected through Students' Motivation towards Science Learning Questionnaire. Two-way Multivariate Analysis of Variance (MANOVA) was conducted to examine the effects of grade level and gender on student motivation (i.e. self efficacy, science learning value, achievement goal and performance goal), active learning strategy use, and learning environment stimulation perceptions. Two-way MANOVA results showed that grade level and gender had a significant effect on the collective dependent variables. Follow-up pairwise comparison indicated that there was a significant difference between 6th and 8th grade students' motivation towards science learning regarding mean scores on each motivational variable. In addition, mean scores on each motivational variable, except leaning environment stimulation, were significantly different for boys and girls, in favors of girls. Results demonstrated that students' motivation towards science learning declined as the grade level increased and girls had a higher motivation towards science learning than boys. (Contains 1 table.)