Pharmacists are essential members of hospital antimicrobial stewardship (AMS) teams. A lack of self-perceived confidence can limit pharmacists' involvement and contributions. Pharmacists working in AMS have reported a lack of confidence. There is currently a lack of validated measures to assess pharmacists' self-perceived confidence when working in AMS and contributors to this confidence. This study aimed to identify variables contributing to pharmacist self-perceived confidence and validate an AMS hospital pharmacist survey tool using confirmatory factor analysis (CFA). Responses from a survey of Australian and French hospital pharmacists were used to undertake CFA and path analysis on factors related to pharmacists' self-perceived confidence. It was hypothesized that pharmacists' self-perceived confidence would be impacted by time working in AMS, perceived importance of AMS programmes, perceived barriers to participating in AMS and current participation. CFA demonstrated a good model fit between the factors. Items included in the model loaded well to their respective factors with acceptable reliability. Path analysis demonstrated that time working in AMS had a significant impact on pharmacists' self-perceived confidence, while perceived barriers had a negatively significant relationship. Pharmacy participation in AMS and perceived importance of AMS programmes had a non-significant impact. Findings demonstrated that the survey tool showed good validity and identified factors that can impact pharmacists' self-perceived confidence when working in hospital AMS programmes. Having a validated survey tool can identify factors that can reduce pharmacists' self-perceived confidence. Strategies can then be developed to address these factors and subsequently improve pharmacists' self-perceived confidence.