The task of generating 3D facial expressions given various situational contexts is important for applications such as virtual avatars or human-robot interactions. The task is, however, challenging not only because it requires a comprehensive understanding of emotion, expression and contexts, but also there rarely are datasets to support the task. We propose ContextFace, a Multi-modal Large Language Model (MLLM) fine-tuned to generate 3D facial expressions depending on complex situational contexts. To overcome the lack of datasets, we perform a context augmentation to existing emotion recognition datasets; we generate plausible situations and quotes from images and emotions to annotate the dataset. Next, we perform visual instruction tuning of MLLMs on context-augmented datasets to boost its capability of visual synthesis from emotions. Experiments show a superior performance of ContextFace in the zero-shot evaluation of contextual emotion recognition. A qualitative evaluation shows that our method generates expressions consistent with diverse contexts and performs complex emotion reasoning, e.g., speculative generation of expressions of occluded faces through interactive prompting.