A multicenter, randomized, double‐blind, placebo‐controlled, efficacy and safety study of BG00012 in participants from the Asia–Pacific region and other countries with relapsing–remitting multiple sclerosis (APEX), including Japan, established the efficacy of dimethyl fumarate (DMF) in preventing relapses and disease progression in patients with multiple sclerosis (MS). Consequently, in December 2016, DMF was approved as the second oral disease‐modifying drug for MS in Japan. However, the new Japanese guidelines for MS and neuromyelitis optica published in 2017 did not include DMF. Later, after the committee discussed a guideline for DMF, a supplement of the new guidelines for MS and neuromyelitis optica, which included DMF, was published in June 2018; this supplement comprised the following four clinical questions: (i) is DMF effective in preventing relapses in patients with MS?; (ii) is DMF effective in preventing disease progression in patients with MS?; (iii) how to use DMF?; and (iv) what adverse events does DMF possibly cause? Furthermore, the supplement comprised answers to the questions and comments. Overall, this supplement is anticipated to contribute toward the treatment of Japanese MS patients with DMF.