Sharing experiences with others, even without communication, can amplify those experiences. We investigated whether shared stressful experiences amplify. Participants completed the Cold Pressor Task at the same time as a confederate, or while the confederate completed another task. Importantly, participants in the shared (vs. unshared) condition experienced more sensory pain characteristics and reported more stress over time in relation to the task. Importantly, they reported thinking more about the confederate’s thoughts and feelings. This mentalizing sometimes mediated effects, suggesting the task amplified when participants constructed mental representations of others’ CPT experience (e.g. that it hurts) and incorporated it into their own responses.