This article explores how English-language learners' writing evolved during a first-year seminar in science course aimed at developing students' argumentation skills. We highlight how a science communications course was paired with a weekly academic English course in the context of a highly coordinated and enriched first-year experience program for international students. This collaborative model provided students with multiple opportunities for discussion and feedback about their writing. An analysis of the data, including student grades and reflections, revealed significant improvements in students' writing structure and abilities to construct evidence-based arguments. Students also perceived positive changes in their critical thinking and specific writing skills for science. This research is a promising example of how collaboration between science and language faculty leads to the development and facilitation of targeted activities and assignments that improve English-language learners' science communication skills in their first year of study at a university.