**Abstract** -------- **Objective:** Having close others present in the emergency department (ED) can cause patients significant distress. The present study tested the hypothesis that close others provide more negative support than non-close others as a potential explanation for this effect. **Design:** Participants were 493 patients evaluated for an acute coronary syndrome (ACS) in the ED (MAge = 62.01, SDAge = 13.55; 49.49% male) and who arrived with close others (i.e., spouse/partner, child) or non-close others (e.g., neighbor). Patients self-reported support from companions (in-hospital) and threat perceptions (in-hospital and at recall approximately three days later). **Main outcome measures:** Positive support (comfort, responsiveness); negative support (made patients anxious, required comforting); threat perceptions (feeling helpless, vulnerable). **Results:** Close (v. non-close) others provided patients with marginally more positive support, but also required more comfort, B = 0.32, p = .050, and caused patients more anxiety, B = 0.24, p = .009. Anxiety was associated with patients’ Threat Perceptions: in-ED, B = 0.11, p = .002; recall, B = 0.14, p < .001; as was provision of comfort to support partners: recall, B = .06, p = .005. **Conclusion:** Negative support may be one mechanism underlying the impact of close others on patient distress in the ED. **Keywords:** posttraumatic stress, close others, emergency department, acute coronary syndrome, social support **Link:** https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6980514/ **Citation:** Cornelius, T., Derby, L., Dong, M., & Edmondson, D. (2020). The impact of support provided by close others in the emergency department on threat perceptions. Psychology & Health, 35(4), 482-499. doi: 10.1080/08870446.2019.1643023