BACKGROUND: The magnitude of cognitive changes after incident heart failure (HF) is unclear. We assessed whether incident HF is associated with changes in cognition after accounting for pre-HF cognitive trajectories and known determinants of cognition. METHODS: This pooled cohort study included adults without HF, stroke, or dementia from 6 US population-based studies from 1971 to 2019. Linear mixed-effects models estimated cognitive change with incident HF diagnosis and the rate of cognitive change over the years after HF, controlling for pre-HF cognitive trajectories and participant factors. Outcomes included change in global cognition (primary outcome), executive function, and memory (secondary outcomes). Cognitive outcomes were standardized to a RESULTS: We included 29 614 adults (mean [SD] age was 61 [10] years, 55% female, 70% White). During a median follow-up of 6.6 (Q1-Q3, 5.0-19.8) years, 1407 (5%) adults received an incident diagnosis of HF. Incident HF diagnosis was associated with initial decreases in global cognition (-1.1 points [95% CI, -1.4 to -0.8]) and executive function (-0.6 points [95% CI, -1.0 to -0.3]). Larger decreases in global cognition after HF were seen with older age, female sex, and White race. Participants with incident HF diagnosis demonstrated faster and long-term declines in global cognition (-0.1 points per year [95% CI, -0.2 to -0.1]) and executive function (-0.2 points per year [95% CI, -0.2 to -0.1]). The change in memory with incident HF diagnosis was not statistically significant but showed a similar trend with an initial decline of -0.5 points (95% CI, -1.4 to +0.3) and a slope of -0.1 points per year (95% CI, -0.3 to 0.0). CONCLUSIONS: In this pooled cohort study, incident HF diagnosis was associated with initial decreases in global cognition and executive function and faster, persistent declines in these domains at follow-up.