Despite interest in how students' implicit theories--their growth and fixed mindsets about their own learning--affect students as learners, relatively little research on mindset has looked at "teachers" as learners. This study explores elementary teachers' implicit theories about the malleability of mathematics intelligence and teaching ability. It also examines how implicit theories of learning relate to teacher noticing, a construct that has been linked to teachers' classroom practice and their students' learning outcomes. Findings from the present investigation indicate that teachers generally reported growth mindsets concerning mathematics intelligence and teaching ability. For both mathematics intelligence and teaching ability, teachers' reporting of more growth--compared to more fixed--mindsets was associated with more expert noticing, as measured by comments they wrote about elementary mathematics video clips on the dimensions of mathematics and student thinking. These findings point to intriguing possibilities about whether fostering growth mindsets (of mathematics intelligence and of teaching ability) in professional development settings might be leveraged to promote expert teacher noticing.