Using a descriptive research design approach, this study investigated the affordances and constraints of a graduate level blended course focused on science teaching and learning. Data were gathered from 24 in-service teacher interviews and surveys. Identified affordances included the structure and implementation of the course, the flexibility of the blended format, and the cohort community. Constraint themes emerged from teachers' beliefs and initial reluctance with online learning, technology skills, and access to technology. Identifying the affordances and constraints of blended courses is valuable for any teacher education program considering a blended model for in-service teacher professional development.