Acknowledging the nearly universal recognition of the significance of context to writing and writing assessment as well as the bedeviling nature of this vague term, this article sketches a theory of context that is at once appropriate to multimodal meaning-making and practicable for multimodal writing assessment. This theory, which insists that texts and contexts are mutually constitutive, reveals the ways in which multimodal texts perform contexts of production and reception. Using a student example, the article models how to assess the performance of context in students’ multimodal writing.