Although diet is thought to affect the natural history of heart failure (HF), nutrient intake in HF patients has not been well studied. Based on prior research linking high intake of Ca, Mg and K to improved cardiovascular health, we hypothesised that these nutrients would be inversely associated with mortality in people with HF. Of the 161 808 participants in the Women's Health Initiative (WHI), we studied 3340 who experienced a HF hospitalisation. These participants were followed for post-hospitalisation all-cause mortality. Intake was assessed using questionnaires on food and supplement intake. Hazard ratios (HR) and 95 % CI were calculated using Cox proportional hazards models adjusted for demographics, physical function, co-morbidities and dietary covariates. Over a median of 4·6 years of follow-up, 1433 (42·9 %) of the women died. HR across quartiles of dietary Ca intake were 1·00 (referent), 0·86 (95 % CI 0·73, 1·00), 0·88 (95 % CI 0·75, 1·04) and 0·92 (95 % CI 0·76, 1·11) (P for trend = 0·63). Corresponding HR were 1·00 (referent), 0·86 (95 % CI 0·71, 1·04), 0·88 (95 % CI 0·69, 1·11) and 0·84 (95 % CI 0·63, 1·12) (P for trend = 0·29), across quartiles of dietary Mg intake, and 1·00 (referent), 1·20 (95 % CI 1·01, 1·43), 1·06 (95 % CI 0·86, 1·32) and 1·16 (95 % CI 0·90, 1·51) (P for trend = 0·35), across quartiles of dietary K intake. Results were similar when total (dietary plus supplemental) nutrient intakes were examined. In summary, among WHI participants with incident HF hospitalisation, intakes of Ca, Mg and K were not significantly associated with subsequent mortality.