To investigate the use, understanding, trust and influence of the internet and other sources of health information used by the next of kin (NOK) of patients admitted to the intensive care unit (ICU). Multicentre structured survey. The ICUs of 13 public and private Australian hospitals. NOK who self-identified as the primary surrogate decision maker for a patient admitted to the ICU. The frequency, understanding, trust and influence of online sources of health information, and the quality of health websites visited using the Health on the Net Foundation Code of Conduct (HONcode) for medical and health websites. There were 473 survey responses. The median ICU admission days and number of ICU visits by the NOK at the time of completing the survey was 3 (IQR, 2-6 days) and 4 (IQR, 2-7), respectively. The most commonly reported sources of health information used very frequently were the ICU nurse (55.6%), ICU doctor (38.7%), family (23.3%), hospital doctor (21.4%), and the internet (11.3%). Compared with the 243 NOK (51.6%) not using the internet, NOK using the internet were less likely to report complete understanding (odds ratio [OR], 0.57; 95% CI, 0.38-0.88), trust (OR, 0.34; 95% CI, 0.19-0.59), or influence (OR, 0.58; 95% CI, 0.38-0.88) associated with the ICU doctor. Overall, the quality of the 40 different reported websites accessed was moderately high. A substantial proportion of ICU NOK report using the internet as a source of health information. Internet use is associated with lower reported understanding, trust and influence of the ICU doctor.