There are approximately 872 certified nurse practitioners (NPs) in Japan as of April 2024. However, research on the results of their specific activities is still scarce. This study aimed to compare health care outcomes before (i.e., 2019) and after (i.e., 2021) employing NPs in cardiovascular hospitals in Japan. We conducted a retrospective chart review and analyzed 114 patients who underwent cardiac surgery in Hospital A and 381 patients who received pacemaker implantation/replacement in Hospital B. Hospital A hired one NP for cardiac surgery service, and Hospital B hired one NP for pacemaker device service. The NPs assisted in the surgical procedures and provided postsurgical management. In Hospital A, the median length of hospitalization and intubation were shorter in 2021 than in 2019 (p = .02 and .01, respectively). In Hospital B, medical fee reimbursement was lower in 2021 (p < .001) than in 2019, and the median procedure duration was shorter (p = .01), which remained statistically significant after controlling for age, comorbidities, and device types. Some outcomes improved following the employment of NPs, whereas others remained unchanged. Nurse practitioners managed surgical patients well and contributed to the quality care of cardiovascular medicine. The employment of NPs in Japan is encouraged because even a single NP can have a positive, although not large, impact on patients and organizations.