OBJECTIVES: To investigate whether partner bereavement is associated with adverse cardiovascular and kidney-related events in people with reduced kidney function. DESIGN: Two parallel matched cohort studies using linked routinely collected health data. SETTING: England (general practices and hospitals using linked Clinical Practice Research Datalink, Hospital Episode Statistics, and Office of National Statistics) and Denmark (hospitals and community pharmacies using the Danish National Patient, Prescription and Education Registries and the Civil Registration System). PARTICIPANTS: Bereaved people with reduced kidney function (estimated glomerular filtration rate (eGFR) <60mL/min/1.73m2 (England) or hospital-coded chronic kidney disease (Denmark)) and non-bereaved people with reduced kidney function similarly defined, matched on age, sex, general practice (England), and county of residence (Denmark) and followed-up from the bereavement date of the exposed person. MAIN OUTCOME MEASURES: Cardiovascular disease (CVD) or acute kidney injury (AKI) hospitalization, or death. RESULTS: In people with reduced kidney function, we identified 19,820 (England) and 5,408 (Denmark) bereaved individuals and matched them with 134,828 (England) and 35,741 (Denmark) non-bereaved individuals. Among the bereaved, the rates of hospitalizations (per 1000 person-years) with CVD were 31.7 (95%-CI: 30.5-32.9) in England and 78.8 (95%-CI: 74.9-82.9) in Denmark; the rates of hospitalizations with AKI were 13.2 (95%-CI: 12.5-14.0) in England and 11.2 (95%-CI: 9.9-12.7) in Denmark; and the rates of death were 70.2 (95%-CI: 68.5-72.0) in England and 126.4 (95%-CI: 121.8-131.1) in Denmark. After adjusting for confounders, we found increased rates of CVD (England, HR 1.06 [95%-CI: 1.01-1.12]; Denmark, HR 1.10 [95%-CI: 1.04-1.17]), of AKI (England, HR 1.20 [95%-CI: 1.10-1.31]; Denmark HR 1.36 [95%-CI: 1.17-1.58]), and of death (England, HR 1.10 [95%-CI: 1.05-1.14]; Denmark HR 1.20 [95%-CI: 1.15-1.25]) in bereaved compared with non-bereaved people. CONCLUSIONS: Partner bereavement is associated with an increased rate of CVD and AKI hospitalization, and death in people with reduced kidney function. Additional supportive care for this at-risk population may help prevent serious adverse events.