Teacher autonomy support and provision of structure are crucial for students' learning and motivation, yet it is unclear how to best blend them. Research describes autonomy support and structure as independent but mutually supportive, equivalent, and even opposite. These contradictions jeopardize the generalizability of findings across studies and hamper classroom implementation. Our meta-analysis aims to disentangle the dynamics between autonomy support and structure by synthesizing their definitions, relationships, and effects on students. Following PRISMA guidelines, 94 studies and 110 effect sizes were identified through databases (PsycINFO, ERIC, Education Research Complete, Psychology and Behavioral Sciences Collection, Teacher Reference Center, ProQuest Education Database, and ProQuest Theses & Dissertations) and forward reference searches. Dissertations and peer-reviewed articles examining teacher autonomy support and structure were included. Our synthesis revealed intertwined conceptualizations and plentiful operationalizations of autonomy support and structure. Autonomy support and structure reinforced each other, with a large effect size. This relationship was moderated by the data collection method and school level and appears to be universal. Autonomy support and structure both elevated students' motivation, engagement, and need satisfaction with moderate to large effect sizes. Teachers who facilitate autonomy and structure were motivated to teach and felt effective as teachers. Our findings suggest blending autonomy support and structure for optimal growth of students and teachers.