Aromatase inhibitors (AIs) are important therapeutic drugs for postmenopausal women with hormone receptor-positive breast cancer. However, adverse effects of AIs such as arthralgia have been extensively reported. We performed a joint prospective, multi-institutional investigation to find out whether a low-dose and short-term prednisolone is effective against AI-induced arthralgia in 27 patients with breast cancer. Patients were administered 5 mg of oral prednisolone once a day in the morning for only one week. Patients were then asked to answer a questionnaire about joint pain symptoms at one week, one month and two months after the beginning of prednisolone use. Joint pain symptoms improved in 67% of patients immediately after prednisolone use, with 63% still reporting analgesic effect at one month, and 52% at two months after beginning internal use of prednisolone. At one week, one month and two months after the use of prednisolone, 30%, 30% and 26% of patients reported improved daily life, respectively. Our results suggest that prednisolone could substitute non-steroidal anti-inflammatory drugs, acetoaminophen or cyclooxygenase-2 inhibitors in patients with AI-induced arthralgia.