This paper explores the role of collaborative teacher agency in facilitating translingual adjustments in a linguistically diverse primary school in Sweden. We focus on three multicompetent language teachers, who taught minoritized languages in the marginalized Mother Tongue (MT) subject, Modern Languages, and offered Multilingual Study Mentoring. Drawing from ethnographic fieldwork, including teacher interviews and fieldnotes from everyday MT practices and preparations for an annual musical performance, we investigated how the teachers adjusted to the students' multilingual repertoires through "relational agency" and "distributed expertise" (Edwards, A. 2011. Building common knowledge at the boundaries between professional practices: Relational agency and relational expertise in systems of distributed expertise. "International Journal of Educational Research" 50(1). 33-39). These adjustments affected the offered language provisions beyond what was required, based on students' linguistic competencies and parental involvement. Didactic adjustments also afforded migrant students literary experiences that starkly contrasted with the limited literacy content in beginner courses in Swedish. These "responsive professional actions" (Edwards, A. 2011. Building common knowledge at the boundaries between professional practices: Relational agency and relational expertise in systems of distributed expertise. "International Journal of Educational Research" 50(1). 33-39, p. 39) thus impacted on the students' opportunities for multilingual development, expanded language registers, including verbal art, and linguistic inclusion. Through these actions, language was reformulated as asset, and we find that "an ethics of care" (Watkins, M. 2011. Teachers' tears and the affective geography of the classroom. "Emotion, Space and Society" 4(3). 137-143) was closely intertwined with this relational agency. The findings contribute new knowledge on the role of collaborative teacher agency in diverse settings also of relevance to other national contexts.