What is known and ObjectiveContinuing education is essential for pharmacists to acquire and maintain the knowledge, skills, and ethical attitudes necessary for clinical practice. However, with the emergence of COVID‐19, the social circumstances and face‐to‐face learning environments have changed. The objectives of this study were to determine Japanese pharmacists’ perception of a web‐based educational programme in oncology, and assess changes in their understanding of pharmaceutical care in oncology before and after their participation in the webinar.MethodsQuestionnaire‐based surveys were conducted for the participants of the web‐based educational programme to determine their perspectives on the webinar, and their degree of comprehension of the five cancer types covered before and after watching the webinar.Results and DiscussionOf the 1936 pharmacists taking the programme, all participated in the pre‐webinar survey, and 1861 (96.1%) in the post‐webinar survey. Compared with previous seminars that were held in the offline mode before the COVID‐19 pandemic, 76.8% of respondents were significantly satisfied with the web‐based educational programme. The median post‐webinar comprehension scores in all modules were significantly higher than the median pre‐webinar scores (p < 0.0001). A majority of the participants agreed that a web‐based educational programme was satisfactory in acquiring knowledge.What is new and ConclusionThis web‐based educational programme was effective for Japanese pharmacists for postgraduate education in pharmaceutical care in oncology. To the best of our knowledge, our study is the first to report the effectiveness of a web‐based educational programme for oncology pharmacists using a large population.