BackgroundUnprofessional behaviours between healthcare workers are highly prevalent. Evaluations of large-scale culture change programs are rare resulting in limited evidence of intervention effectiveness. We conducted a multi-method evaluation of a professional accountability and culture change program “Ethos” implemented across eight Australian hospitals. The Ethos program incorporates training for staff in speaking-up; an online system for reporting co-worker behaviours; and a tiered accountability pathway, including peer-messengers who deliver feedback to staff for ‘reflection’ or ‘recognition’. Here we report the final evaluation component which aimed to measure changes in the prevalence of unprofessional behaviours before and after Ethos.MethodsA survey of staff (clinical and non-clinical) experiences of 26 unprofessional behaviours across five hospitals at baseline before (2018) and 2.5–3 years after (2021/2022) Ethos implementation. Five of the 26 behaviours were classified as ‘extreme’ (e.g., assault) and 21 as incivility/bullying (e.g., being spoken to rudely). Our analysis assessed changes in four dimensions: work-related bullying; person-related bullying; physical bullying and sexual harassment. Change in experience of incivility/bullying was compared using multivariable ordinal logistic regression. Change in extreme behaviours was assessed using multivariable binary logistic regression. All models were adjusted for respondent characteristics.ResultsIn total, 3975 surveys were completed. Staff reporting frequent incivility/bullying significantly declined from 41.7% (n = 1064; 95% CI 39.7,43.9) at baseline to 35.5% (n = 505; 95% CI 32.8,38.3; χ2(1) = 14.3; P < 0.001) post-Ethos. The odds of experiencing incivility/bullying declined by 24% (adjusted odds ratio [aOR] 0.76; 95% CI 0.66,0.87; P < 0.001) and odds of experiencing extreme behaviours by 32% (aOR 0.68; 95% CI 0.54,0.85; P < 0.001) following Ethos. All four dimensions showed a reduction of 32–41% in prevalence post-Ethos.Non-clinical staff reported the greatest decrease in their experience of unprofessional behaviour (aOR 0.41; 95% CI 0.29, 0.61). Staff attitudes and reported skills to speak-up were significantly more positive at follow-up. Awareness of the program was high (82.1%; 95% CI 80.0, 84.0%); 33% of respondents had sent or received an Ethos message.ConclusionThe Ethos program was associated with significant reductions in the prevalence of reported unprofessional behaviours and improved capacity of hospital staff to speak-up. These results add to evidence that staff will actively engage with a system that supports informal feedback to co-workers about their behaviours and is facilitated by trained peer messengers.