Introduction: Although there have been several national survey studies on complementary and alternative medicine (CAM) use in Japan, previous studies have not been compared with investigations conducted in other countries. An international CAM questionnaire known as I-CAM-Q was developed through a two-day international workshop in 2006. The purpose of this study was to investigate the use of CAM by the general Japanese population using a modified version of the I-CAM-Q for the Japanese (I-CAM-QJ). Methods: We developed the I-CAM-QJ to conduct an internet survey of 3,208 participants from the general population of Japan in February 2016. The respondents included 1,592 males (49.6%), 1,348 university graduates (38.8%), 1,105 individuals in good health (34.4%), and 1,028 individuals with long-term illness or disability (32.0%). Results: Of the 3,208 respondents, 411 participants reported CAM use during the past 12 months (12.8%). The following therapies and products were used: Kampo medicines (over-the-counter Kampo medicines: 15.7%; prescribed Kampo medicines: 15.4%), dietary supplements 11.8%, massage services 3.9%, and physical therapy 3.5%. Regarding the use of self-care methods during the last 12 months, the following methods and products were used: bath salts 25.8% and walking 25.3%. Conclusions: An internet survey on CAM use by the general Japanese population with a modified I-CAM-Q (I-CAM-QJ) revealed that Kampo medicines and dietary supplements were the most commonly used CAMs in Japan.