Despite the recent attention given to palliative care for patients with heart disease, data about the treatments in their actively dying phase are not sufficiently elaborated. In this study, we used the sampling dataset of a national database to compare the aggressive treatments performed in patients with cancer and those with heart disease. We only included patients deceased in January or July from 2011 to 2015, using the Diagnosis Procedure Combination sampling dataset of the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). Patients who were discharged within the first 10 days of each month were excluded. We explored and compared aggressive treatments such as cardiopulmonary resuscitation and intensive care utilization, performed within seven days before death in cancer patients. We used 10,637 (0.4% of the dataset) deceased target population (40.0% female), with 7844 (73.7%) and 2793 (26.3%) being the proportion of cancer and heart disease patients, respectively. Aggressive treatments and procedures such as cardiopulmonary resuscitation (18.4%), intensive care utilization (5.4%), use of inotropes (43.4%), use of respirators (29.1%), and dialysis (4.5%) were frequently observed in heart disease patients. These associations remained after adjusting for age, sex, and disease severity. This study indicates the possible use of an NDB sampling dataset to evaluate the aggressive treatments and procedures in the actively dying phase in both heart disease and cancer patients. Our results showed the differences in aggressive treatment strategies in the actively dying phase between patients with cancer and those with heart disease.