Protein diversity refers to the consumption of a variety of protein sources to meet nutritional needs (1). Current evidence suggests that higher total protein intake is associated with a lower risk of all-cause mortality in older populations (2), though the relationship between dietary protein diversity and mortality in older adults (70+ years) is not well understood (3). This study examined associations between protein diversity and all-cause and cause-specific mortality in older adults. This prospective cohort study involved 10,194 participants from the ASPREE Longitudinal Study of Older Persons (ALSOP). Participants completed a 49-item Food Frequency Questionnaire, from which consumption of protein foods was ascertained, including dairy, meat, and plant-based sources. Protein Diversity Scores (PDS) were created, representing the number of protein foods consumed weekly, ranging from 0 to 12. Subgroups exploring weekly protein foods across usual dietary patterns (meat-based, plant-based, lacto-ovo vegetarian, pescatarian, and fish-based) were also established. All-cause death was ascertained from at least two sources: medical records, death notices, next of kin, or death registry linkage. Cause-specific (cardiovascular disease [CVD] and cancer) mortality was adjudicated from medical history and records. Associations were assessed using Cox proportional hazards regression, adjusted for sociodemographic, health-related, clinical, and dietary quality factors. Over a mean follow-up of 8.0 years (SD 1.9), 2,242 participants (22.0%) died, including 840 (8.2%) from cancer and 556 (5.5%) from CVD. Of the included participants, 720 (7.6%) reported low (0–3 foods/week), 7,882 (77.2%) medium (4–8 foods/week), and 1,592 (15.6%) high (9–12 foods/week) total weekly PDS. Compared with low PDS, high PDS was associated with a 24% lower risk of all-cause mortality (HR: 0.76, 95% CI 0.63–0.92) and a 31% lower risk of CVD mortality (HR: 0.69, 95% CI 0.48–0.99); no association was observed with cancer mortality. Subgroup analyses indicated that plant-based, pescatarian, and lacto-ovo-vegetarian protein patterns may be associated with lower earlier mortality risk than meat protein patterns. This study found that higher weekly protein diversity was associated with a lower risk of all-cause and CVD mortality in older adults. Protein patterns emphasising non-meat and poultry sources were generally associated with lower early mortality risk. Together, these findings suggest that protein variety, alongside quantity, may support longevity and healthy ageing.