ObjectivesTo explore the awareness and practice of clinical research integrity among Japanese physicians.DesignA nationwide cross-sectional study conducted in March 2020.SettingAll hospitals in Japan.ParticipantsPhysicians aged <65 years who work at hospitals participated in clinical research over the past 5 years. The sample was stratified according to geographical location and subspecialty, and 1100 physicians were proportionally selected.Primary and secondary outcome measuresKnowledge and awareness of research integrity.ResultsAmong the 1100 participants, 587 (53%) had the experience of being the first author, 299 (27%) had been co-authors only and 214 (19%) had no authorship. A total of 1021 (93%) had experienced learning research integrity, and 555 (54%) became aware of research integrity. The experience of learning about research integrity was highest among those with first authorship (95%) and lowest among those without authorship (89%) (p=0.003). The majority of participants learnt about research integrity for passive reasons such as it being ‘required by the institution’ (57%) or it being ‘required to obtain approval of institutional review board (IRB)’ (30%). Potentially inappropriate research behaviours were observed in participants, with 11% indulging in copying and pasting for writing the paper, 11% for gifted authorship and 5.8% for the omission of IRB approval. Factors significantly associated with copying and pasting were being below 40 years old (OR: 1.84; 95% CI: 1.05 to 3.26), being the first presenter (OR: 1.64; 95% CI: 1.05 to 2.57) or having passive reasons for learning research integrity (OR: 2.96; 95% CI: 1.57 to 5.59). Furthermore, gifted authorship was significantly associated with being a co-author only (OR: 1.84; 95% CI: 1.18 to 2.87) and having passive reasons for learning about research integrity (OR: 1.79; 95% CI: 1.03 to 3.12).ConclusionsMost physicians conducting clinical research have learnt about research integrity, but potentially inappropriate research behaviours are associated with passive reasons for learning.