Resuscitation in the oldest old at the end of life is associated with potential harm, raising concerns about misalignment with patients goals of care. This study aimed to elucidate changes in the use of resuscitation among the oldest old in Japan following the revision of the national guideline on end-of-life care which explicitly incorporates the concept of advance care planning. We conducted a repeated cross-sectional study using the National Database of Health Insurance Claims Open Data, including adults aged [≥]85 years, from April 2014 to March 2024. The annual number of resuscitation procedures per 100,000 individuals aged [≥]85 years was used as the measure of frequency. Resuscitation included closed-chest cardiopulmonary resuscitation (CPR) and endotracheal intubation. Interrupted time series analysis was used to examine changes following the 2018 revision of the national end-of-life care guideline. The frequencies of CPR and endotracheal intubation declined before 2018 (CPR: age 85-89, -68.4 [-87.9 to -48.8]; age [≥]90, -106.7 [-131.5 to -82.0]; intubation: age 85-89, -57.5 [-71.8 to -43.2]; age [≥]90, -69.5 [-80.7 to -58.3]), but the decline attenuated thereafter (CPR: age 85-89, +56.2 [28.0 to 84.5]; age [≥]90, +84.1 [50.7 to 117.6]; intubation: age 85-89, +36.6 [8.5 to 64.7]; age [≥]90, +38.3 [23.8 to 52.8]). These findings provide insight into the changes in resuscitation trends following policy interventions supporting end-of-life decision-making. Further studies are needed to better understand the mechanisms underlying this change.