Background Development of a critical mass of evidence‐based practice (EBP) mentors for healthcare professionals is pivotal in facilitating and sustaining system‐wide implementation of evidence‐based care, especially for nurses. Empirical evidence shows that organizational factors are strongly associated with EBP. However, the understanding of organizational support to promote EBP competency is found lacking, especially in Mainland China. Aims The purposes of this study were to (1) establish a baseline assessment of EBP nursing leadership and work environment support as well as EBP competency for EBP mentors of nurses in Western China, and (2) explore how nursing leadership and work environment impact the EBP competencies of mentors. Methods A cross‐sectional study was conducted. The study population was 286 EBP mentors for nurses from six urban general hospitals in Xi’an City, Shanxi Province. The EBP Nursing Leadership Scale and the EBP Work Environment Scale were used to evaluate their perceived organizational support. EBP competency was measured by the Evidence‐Based Practice Questionnaire. Results There was insufficient time for EBP mentors of nurses to engage in EBP. Lack of experts in EBP and educational offerings about EBP were identified as the two lowest workplace organizational supports for EBP. The respondents reported themselves as not competent in EBP, especially for the knowledge/skills. EBP nursing leadership and work environment support were key predictors of the self‐reported EBP competency in the stepwise multiple linear regression models (β = .211–.345, p < .01). Linking Evidence to Action It is imperative to provide EBP mentors for nurses with the knowledge and skills to achieve the expected level of EBP competency. Strategies for developing a cadre of EBP mentors for nurses who have competency in EBP need to be multipronged and target the cultivation of an organizational culture that supports EBP.