Abstract Backgrounds: We organized WEBINAR focusing on treatment and nursing of MBC for the first time in Japan. The purpose of this study is to investigate the learning effect to the nurses who attended this program and to verify the effectiveness of this educational program. Material and Methods: This educational program consists of 13 chapters and each chapter contains lecture and case studies of 15 to 20 minutes length. It includes pathophysiology and treatment of MBC and special nursing for special condition of MBC, i.e. breast ulceration and bone metastasis with severe pain. The target audience is nurses with more than three years of breast cancer nursing experience. Educational program has been developed in cooperation with Certified Nurses in Breast Cancer Nursing, Certified Nurse Specialists in Cancer Nursing, pharmacists and a doctor. Teaching material was composed of several slides with commentary. It was distributed on-demand for free from November 2016 for three months. Eighty-five nurses who gave consent to this investigation from 771 participants of this program were analyzed for the correlation of learning effect of this program with their background. Also, each program was assessed in terms of effectiveness. Twenty six questions (two questions each for one program) were asked via the internet before and after the program (one question 1 point). The average of total score before and after the program was analyzed. In addition, we analyzed individual characteristics affecting the total score before and after the program by a two way factorial analysis of variance. Furthermore, we assessed the rate of change of the participants number who have given right answers (calculation formula: (number of participants with correct answer after program - before program) / number of participants with correct answer before program). This study was approved in the ethics committees of Chiba University Graduate School of Nursing Graduate School. Results: Median age was 42.0 years, and median period of breast cancer nursing experience was 4.7 years. Average total score before and after the program was 20.5 points and 23.0 points respectively. There was no statistical significant correlation between individual characteristic with learning effect. The most effective chapter was “Treatment strategy of MBC (rate of change: 54%)”, followed by “Nursing of HBOC (40%)” and “Medication of MBC (34%)”. On the other hand, several chapters on nursing for MBC have low change rate (7%). Conclusion: The participants have deepened their understanding of pathophysiology, treatment and nursing on MBC through this program. It provided good opportunity to learn about MBC for many nurses, and improved their level of nursing. This work was supported by JSPS KAKENHI(Grant Number 16K20748.) Citation Format: Iseki C, Abe K, Nakayama T, Arahori Y, Ookawa M, Kasatani M, Kabazawa M, Tobata R, Fujii C. Effectiveness of education program of WEBINAR focusing on treatment and nursing for metastatic breast cancer patients (MBC) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-16-04.