The aim of this study was to assess the role of the patient's background and perceived healthcare-related factors in symptoms of acute stress after lung cancer diagnosis.The study population consisted of 89 individuals referred for diagnostic work-up at Landspitali National University Hospital in Iceland and subsequently diagnosed with lung cancer. Before diagnosis, the patients completed questionnaires on sociodemographic characteristics, pre-diagnostic distress (Hospital Anxiety and Depression Scale), social support, and resilience. At a median of 16 days after diagnosis, the patients reported symptoms of acute stress on the Impact of Event Scale-Revised (IES-R) and experience of communication and support from healthcare professionals and family during the diagnostic period.Patients were on average 68 years and 52% reported high levels of post-diagnostic acute stress (IES-R > 23) while 24% reported symptoms suggestive of clinical significance (IES-R > 32). Prior history of cancer (β = 6.7, 95% CI: 0.1 to 13.3) and pre-diagnostic distress were associated with higher levels of post-diagnostic acute stress (β = 8.8, 95% CI: 2.7 to 14.9), while high educational level (β = - 7.9, 95% CI: - 14.8 to - 1.1) was associated with lower levels. Controlling for the abovementioned factors, the patients' perception of optimal doctor-patient (β = - 9.1, 95% CI: - 14.9 to - 3.3) and family communication (β = - 8.6, 95% CI: - 14.3 to - 2.9) was inversely associated with levels of post-diagnostic acute stress after lung cancer diagnosis.A high proportion of patients with newly diagnosed lung cancer experience high levels of acute traumatic stress of potential clinical significance. Efforts to improve doctor-patient and family communication may mitigate the risk of these adverse symptoms.© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.