Professional development on issues of language and culture is often separate from professional development on issues related to STEM education, resulting in linguistic and cultural gaps in K-12 STEM pedagogy and practice. To address this issue, we have designed a model of professional development in which we work with educators to build cultural and linguistic competence and to disseminate information about how educators view the relevance of language, communication, and culture to STEM teaching and learning. We describe the design and facilitation of our model of culturally and linguistically responsive professional development, grounded in theories of multicultural education and culturally supportive teaching, through professional development workshops to 60 K-12 STEM educators from schools in Maryland and Virginia that serve African American students. Participants noted that culturally and linguistically responsive approaches had yet to permeate their K-12 STEM settings, which they identified as a critical challenge to effectively teaching and engaging African-American students. Based on pre-surveys, workshops were tailored to participants' stated needs for information on literacy (e.g., disciplinary literacies and discipline-specific jargon), cultural conflict and mismatch (e.g., student-teacher miscommunication), and linguistic bias in student assessment (e.g., test design). Educators shared feedback via post-workshop surveys, and a subset of 28 participants completed in-depth interviews and a focus group. Results indicate the need for further implementation of professional development such as ours that address linguistic and cultural issues, tailored for K-12 STEM educators. Although participants in this study enumerated several challenges to meeting this need, they also identified opportunities for collaborative solutions that draw upon teacher expertise and are integrated with curricula across content areas.