AbstractINTRODUCTIONWidowhood and divorce are extremely stressful life events that are associated with dementia, but the neurobiological underpinnings of this risk remain unknown. Amyloid beta (Aβ) load may explain influences of chronic stress, commonly seen in disruptive marital transitions, on cognitive decline.METHODSWe examined whether Aβ quantified by tracer uptake on positron emission tomography mediates associations between marital dissolution and executive functioning and episodic memory performance using data from 543 cognitively normal (CN) participants from the Alzheimer's Disease Neuroimaging Initiative.RESULTSMarriage dissolution was associated with increased Aβ burden (β = 0.56; P = 0.015) and worse memory performance (β = –0.09; P = 0.003). Aβ levels were a significant mediator for the relationship between marriage dissolution and memory (average causal mediation effect = –0.007; P = 0.029).DISCUSSIONFindings suggest that stressful life events, such as the dissolution of one's marriage, might exert an effect on Alzheimer's disease proteinopathy, which may subsequently influence poor cognition.Highlights Marital dissolution was associated with increased amyloid beta (Aβ) and memory declines. Aβ burden mediated associations between marital dissolution and memory. Findings were robust to potential non‐linear influences of age. Mediation results were not observed when stratifying marital groups by sex.