Aims The presence of diabetic foot ulcers is strongly associated with an increased risk of death. In this study, we investigate whether the effects of diabetes‐associated complications can explain the apparent relationship between diabetic foot ulcers and death. Methods We analysed data from 414 523 people with diabetes enrolled in practices associated with The Health Improvement Network in the United Kingdom. Our methods were designed to control for potential confounders in order to isolate the relationship between diabetic foot ulcers and death. Using proportional hazards models and the area under the receiver operator curve, we evaluated the effects of diabetic foot ulcers and the covariates on death. Results Among the patients, 20 737 developed diabetic foot ulcers; 5.0% of people with new ulcers died within 12 months of their first foot ulcer visit and 42.2% of people with foot ulcers died within 5 years. After controlling for major known complications of diabetes that might influence mortality, the correlation between diabetic foot ulcers and death remained strong with a fully adjusted hazard ratio of 2.48 (95% confidence interval: 2.43, 2.54). Geographic variance existed but was not spatially associated. Conclusions Diabetic foot ulcers are linked to an increased risk of death. This cannot be explained by other common risk factors. These results suggest that either there are major unknown risk factors associated with both diabetic foot ulcers and death, or that diabetic foot ulceration itself is a serious threat, which seems unlikely. A diabetic foot ulcer should be seen as a major warning sign for mortality, necessitating closer medical follow‐up. What's new? This is the largest patient cohort study ever to study the association between diabetic foot ulcers and risk of death in adults with diabetes. Our findings support the hypothesis that diabetic foot ulcers are a marker associated with a risk to patients’ longevity independent of other complications of diabetes.