Aim: Expected 1-year survival is essential to risk stratification of patients with heart failure (HF); however, little is known about the 1-year prognosis of patients with HF and cancer. Thus, the objective was to investigate the 1-year prognosis following new-onset HF stratified by cancer status in patients with breast, gastrointestinal, or lung cancer. Methods and results: All Danish patients with new-onset HF from 2000 to 2018 were included. Cancer status was categorized as history of cancer (no cancer-related contact within 5 years of HF diagnosis), non-active cancer (curative intended procedure administered) and active cancer. Standardized 1-year all-cause mortality was reported using G-computation. Age-stratified 1-year all-cause mortality was estimated using the Kaplan–Meier estimator. In total, 193 359 patients with HF were included, 7.3% had either a breast, gastrointestinal, or lung cancer diagnosis. Patients with cancer were older and more comorbid than patients without cancer. Standardized 1-year all-cause mortality (95% confidence intervals) was 24.6% (23.0–26.2%), 27.1% (25.5–28.6%), and 29.9% (25.9–34.0%) for history of breast, gastrointestinal and lung cancer, respectively, which was comparable to patients with non-active cancers. For active breast, gastrointestinal and lung cancer, standardized 1-year all-cause mortality was 36.2% (33.8–38.6%), 49.0% (47.2–50.9%), and 61.6% (59.7–63.5%), respectively. One-year all-cause mortality increased incrementally with age, except for active lung cancer. Conclusion: Standardized 1-year all-cause mortality was comparable for patients with history of cancer and non-active cancer regardless of cancer type, but varied comprehensively for active cancers. Prognostic impact of age was limited for active lung cancer. Thus, granular stratification of cancer is necessary for optimized management of new-onset HF.