This is a qualitative case study framed by a sociosemiotic theoretical framework to explore science and language instruction with three Emergent Bilinguals (EBs) in sixth grade. The study details the modeling and explanatory processes used by EBs to mediate science learning through evidence-based argumentation. A thematic analysis of students' models, explanations and arguments was conducted. Three themes emerged from the analysis: (1) modeling and explanatory processes evolved from illustrative to causal purpose, (2) students engaged in discursive practices similar to scientific communities, and (3) students mediated science learning through evidence-based argumentation. The three themes revealed that when EBs are taught through integrated science and language instruction they are provided with opportunities to approximate the discipline-specific language register of science through three language functions: ideational, interpersonal and textual. Modeling and explaining scaffolded evidence-based argumentation tasks through which EBs critiqued each other's models and explanations and revised their conceptual understanding of science concepts to increase sense-making. Implications suggest integrated content and language instruction to provide students with experiential learning opportunities while affording discourse and interactive opportunities on a larger scale and via other research methodologies to include a larger sample size of EBs.