Abstract Background: The patient experience of atrial fibrillation (AF) involves several daily self-care behaviors and ongoing confidence to manage their condition. Currently, no standardized self-report measure of AF patient confidence exists. The purpose of this study is to establish the reliability and validity of a newly developed confidence in AF management measure. Methods: This study provides preliminary analysis of the Confidence in Atrial FibriLlation Management (CALM) scale, which was rationally developed to measure patient confidence related to self-management of AF. The scale was provided to a sample of AF patients N=120, (59% male) electronically through a patient education platform. Principle components analysis (PCA) and Cronbach’s alpha were employed to provide preliminary assessment of the validity and reliability of the measure. Results: PCA identified a four-factor solution. Internal consistency of the CALM was considered excellent with Cronbach’s α = .910. Additional PCA confirmed the value of a single factor solution to produce a total confidence score for improved utility and ease of clinical interpretation. Conclusions: Initial assessment of a novel scale measuring patient confidence in managing AF provided promising reliability and validity. Patient confidence in self-management of AF may prove useful as a key marker and endpoint of the patient experience beyond QOL.