As the vision in "A Framework for K-12 Science Education" and the Next Generation Science Standards (NGSS) takes hold in schools and classrooms, there is an urgent need for teacher professional development (PD) programs that align with NGSS-designed curriculum materials and address the unique strengths and needs of diverse student groups, including multilingual learners (MLs). The purpose of this article is to propose our conceptual framework for PD programs that aligns with current reform efforts and is grounded in the mutually supportive nature of contemporary science and language instructional shifts. Specifically, we examine our previous NGSS-designed curriculum development project with MLs and review the literature in science education and language education with MLs. Our conceptual framework for PD programs is grounded in the perspective of "symmetry" that teacher professional learning experiences should be symmetrical to the learning experiences we organize for students. Grounded in this perspective, our conceptual framework consists of three design principles that describe how PD programs can guide teachers to (a) develop an asset-oriented view of MLs and instructional practices for recognizing and leveraging their assets, (b) integrate science and language in mutually supportive ways with MLs, and (c) develop more sophisticated instructional practices for integrating science and language with MLs over time. We describe contributions of our conceptual framework, which could generate a new research agenda and inform PD programs aimed at facilitating uptake of NGSS-designed curriculum materials in linguistically diverse science classrooms.