Family size matters. As a family grows, parents dedicate less time as well as financial and emotional support to each child. Siblings often have to compete for parental resources whereas only children receive full support from parents throughout their lives. Previous research has found that competition leads people to adopt performance goals (i.e., motivation to perform better than others). In big families, competitive environments may signal that being more successful than others is important, making performance goals more salient than in a family where one is the only child, where mastery goals (i.e., motivation to master new skills) may be more salient. In an exploratory study, we examined whether family size shapes people’s motivations for learning. We predicted that students with siblings would be more motivated to learn by competing with others (performance orientation) while only children would be more motivated by honing their skills (mastery orientation). To test this hypothesis, we recruited 328 participants (166 only children and 162 with siblings) for an online study in which they completed the Achievement Goal Questionnaire and provided information about their race and number of siblings. As predicted, only children more strongly endorsed mastery orientation (M=3.93, SD=.58) compared to students with siblings (M=3.80, SD=.62, t(326)=1.99, p=0.5). Students with siblings endorsed performance orientation (M=4.05, SD=.78) marginally more than only children (M=3.90, SD=.73, t(326)=1.90, p=.06). While further research is needed to understand why these differences emerge (e.g., due to competition or other differences in family environments), our study lends insight into how people’s family experiences shape their academic motivation. These findings many help educators learn how to best motivate students from different types of families.