Background Families of intensive care unit (ICU) decedents are at increased risk of experiencing complicated grief. However, factors associated with complicated grief in ICU and bereavement needs assessment are not available routinely. We aimed to conduct a systematic review identifying risk factors associated with complicated grief among family members of ICU decedents. Materials and methods MEDLINE, EMBASE, CINAHL, PsycINFO, the Cochrane Library and Web of Science were searched to identify relevant articles. Observational studies and randomised and non-randomised controlled trials were included. Studies were screened and quality appraised in duplicate. Risk of bias was assessed using Newcastle-Ottawa Scale. A narrative synthesis was undertaken. Results Seven studies conducted across three continents were eligible. Four studies were of high quality. 61 risk factors were investigated across the studies. Factors associated with a decreased risk of complicated grief included age, patient declining treatment and involvement in decision-making. Factors associated with increased risk included living alone, partner, dying while intubated, problematic communication, and not having the opportunity to say goodbye. Conclusion This systematic review has identified risk factors which may help identify family members at increased risk of complicated grief. Many of the studies has small sample sizes increasing the risk of erroneously reporting no effect due to type II error. Some factors are specific to the ICU setting and are potentially modifiable. Bereavement services tailored to the needs of bereaved family members in ICU settings are required. (PROSPERO registration ID 209503)