Much research has examined the role of writing in science learning, but most of this work has focused on print-based expository writing. Much less work has explored multimodal narratives in science education. We designed a program that aims to engage adolescents in producing multimodal sci-fi narratives. In this study, we focused on analyzing the products students generated as a way to assess how students integrate science in their multimodal narratives. More specifically, we developed an assessment framework that includes two dimensions (science and integration). We applied this framework to assess the 35 products produced by 130 participants in 5 iterations of the program. The results show that about half of the products presented high quality in science integration. Multiple mechanisms were employed in these products to integrate science in their narratives. Instructional implications are also discussed.