Advancing Equity and Strengthening Teaching with Elementary Mathematical Modeling is a teacher PD project focused on strengthening K-5 teaching with mathematics modeling. Building on previous foundational work around mathematics modeling and equity, this project will bring together equity oriented teaching practices and mathematical modeling to design and research the impact of a blended PD program on teacher practice. The project will include video-enhanced reflection and online mentoring in addition to face-to-face components of PD. Using five pivotal spaces for elementary mathematics modeling as a framework, the project will explore the ways in which tools and structures that support practices aligned with pivotal spaces in mathematics modeling lessons can help teachers advance equitable participation and develop student competencies in mathematics modeling. The project will engage in cycles of design-based implementation research (DBIR) to study the relationships between features of the PD and changes in teacher practice, understandings, and dispositions.