Telemedicine, or online medical care, has gained considerable attention worldwide. However, it has not been widely adopted in Japan, and the detailed status of received and provided online medical care and the reasons for its lack of popularity remain unknown. This study aims to investigate the current status of online medical care in Japan and the factors limiting its adoption from the perspective of both patients receiving and medical professionals providing online medical care. In total, 2 nationwide questionnaire surveys were conducted. The first survey, targeting both patients and healthy individuals, screened approximately 40,000 participants among 13 million people. The participants were selected to match the age distribution of the Japanese population based on government data, and their online medical care experience and medical visit status were recorded. To further investigate online medical care use and satisfaction, a web-based survey was conducted with 15% (6000/40,000) of the screened participants. The second survey, targeting medical professionals, was administered to a physician, a nurse, and a member of the administrative staff in each of 4900 randomly selected medical facilities to inquire about their online medical care practices and impressions. In addition, both surveys investigated the factors limiting online medical care expansion in Japan. The response rates among patients and healthy individuals targeted for the screening and main surveys were 92.5% (36,998/40,000) and ˃80% (1312/1478, 88.77%; 1281/1522, 84.17%; 404/478, 84.5%; and 2226/2522, 88.26% in 4 survey groups), respectively. The survey of medical professionals yielded 1552 responses (n=618, 39.82% physicians; n=428, 27.58% nurses; n=506, 32.6% administrative staff). Although the facility-level response rate was low (794/4900, 16.2%), some facility categories had relatively high response rates. Only 5.29% (1956/36,998) of the patients and healthy individuals had online medical care experience. When there were more hospitals nearby and they felt it was more work to see a physician in person, they were more likely to use online medical care (more nearby hospitals: adjusted odds ratio [aOR] 1.33, 95% CI 1.18-1.50; more work: aOR 1.48, 95% CI 1.35-1.63 per survey response point in the patient group). Similarly, these factors were substantially associated with satisfaction (more nearby hospitals: aOR 1.40, 95% CI 1.14-1.73; more work: aOR 1.50, 95% CI 1.27-1.76 per survey response point in the patient group). In both surveys, the most frequently selected factor preventing the widespread use of online medical care was patients' need to switch to face-to-face medical care for mandatory tests and procedures. Inadequate awareness of and education on online medical care were also frequently selected. Our nationwide surveys provided insights into the current status of online medical care in Japan and simultaneously identified several problems and issues related to it, which will be useful in promoting its wider adoption.