Background: Bereavement is associated with a risk of poor mental health and suicide. Contemporary theories of grief describe it as a dynamic process, in which the aftermath is the most difficult stage, but with periods of oscillating between loss and restoration over the course of the assimilation trajectory. Anniversary reactions are conceptualised as psychological, somatic and behavioural reactions to an anniversary of a substantial past event. Our systematic review aimed to summarise the findings from the scientific literature investigating whether there is evidence to support anniversary reactions in the form of suicidal behaviours after bereavement by any cause. Method: An electronic search was performed in 6 databases: MEDLINE, Scopus, EMBASE, Web of Science, PsycInfo and PROQuest. Following PRISMA guidelines, three selection filters were independently conducted by two authors: at the level of titles, at the level of abstracts, and at the level of full-text articles. Eligible articles were independently assessed for study quality using the JBI critical appraisal tools. Results: After deduplication, we identified and screened a total of 3,945 papers, identifying a total of 55 eligible articles focusing on anniversaries reactions, of which 5 reported on suicidal behaviours. The analyses of UK registry data (1971), Australian mortality data (2014), and Swedish registry data (2022, 2023) reported a significant increase in suicidal behaviours around anniversaries, including death by suicide in three studies. Anticipatory anniversary reactions were reported in the weeks preceding the anniversary dates. Women tended to be more vulnerable towards suicidal behaviours around bereavement anniversaries in three of the studies. The analysis of Danish registry (2023) reported no increased rate of suicide or medically serious self-harm around the time of anniversaries of the birth of death of the deceased, whether for suicide-bereaved or other-bereaved individuals. An analysis of Swedish registry data reported a significantly reduced risk of suicide in men on anniversaries of a parent’s death (2023). Conclusion: The scientific literature supports the hypothesis of increased risk of suicidal behaviours, including suicide, at anniversaries after bereavement. Findings differ by gender, with women more vulnerable and men in one large study showing a reduced risk of suicide around anniversaries. Whether suicide risk is elevated in men or women around anniversaries of suicide deaths needs further investigation in larger samples. There is an apparent need for t