Through secondary analysis of data collected in middle school science classrooms, this study (a) compared gifted and regular students' beliefs about the malleability of intelligence in science; (b) investigated whether teaching gifted and talented middle-school students about malleability of the brain and study skills helped them to develop a growth mindset (Dweck, 2000), and (c) examined whether there were teacher effects in the impact of the intervention. Compared to the general student population, gifted and talented students were more likely to endorse the idea that intelligence is malleable, but there was considerable variability among gifted students' mindset beliefs. Results of a mixed between-within subjects ANOVA showed a large effect size in the impact of the six week mindset intervention (Brainology) among the gifted and talented students. While strong teacher effects on growth mindset were found among students in the general population who participated in the intervention, similar teacher effects were not found among the gifted and talented students. A growth mindset is particularly important for gifted students because they are at risk for both under-achievement and perfectionism, which may hinder them from reaching their potential.