BackgroundComplementary medicine (CM) is utilized in a growing number of academic centers despite the debate concerning its value, risks and benefits. Healthcare professionals often feel uncomfortable discussing CM with patients, and little is known about their sources of knowledge in the field of CM.ObjectiveTo assess healthcare professionals’ sources of knowledge and attitude toward CM in an academic hospital.Design and participantsThe cross-sectional web-based survey took place from October to December 2013. A total of 4,925 healthcare professionals working at Lausanne University Hospital, Switzerland, were invited to answer the questionnaire.Main measuresFactors influencing healthcare professionals’ opinion toward CM, knowledge and communication about CM.Key resultsThe questionnaire was answered by 1,247 healthcare professionals. The three key factors influencing professionals’ opinion toward CM were personal experience, clinical experience and evidence demonstrating the physiological mechanism of CM. Personal experience was more associated with nurses’ and midwives’ opinion compared to physicians’ (80.8% vs 57.1%, OR = 3.08, [95% CI: 2.35–4.05], P<0.001 and 85.3% vs 57.1%, OR = 3.83, [95% CI: 1.95–7.53], P<0.001, respectively) as well as with professionals trained in CM compared to non-trained professionals (86.0% vs 73.2%, OR = 2.60, [95% CI: 1.92–3.53], P<0.001). Physicians relied more on randomized controlled clinical trials compared to nurses (81.3% vs 62.9%, OR = 0.43, [95% CI: 0.33–0.57], P<0.001). A majority of the respondents (82.5%) agreed that they lacked knowledge about CM and 65.0% noted that it was the patient who initially started the discussion about CM.ConclusionsDifferent professionals used different strategies to forge opinions regarding CM: physicians relied more on scientific evidence, while nurses and midwives were more influenced by personal experience. Regardless of preferred information source, most respondents did not feel prepared to address patient questions regarding CM. Enhancing interprofessional education opportunities is an important strategy to help providers become empowered to discuss CM with patients. This in turn will help patients making informed decisions in their healthcare.