The 10-item Cognitive Fusion Questionnaire-Body Image (CFQ-BI; Ferreira et al., 2015) assesses cognitive fusion related to body image, which represents an entanglement with cognitions related to one’s body, perceiving them as true events of reality instead of subjective and transitory experiences. In other words, an individual becomes “fused” with their internal events (e.g., thoughts, emotions, memories, sensations) concerning body image and is highly regulated by them. Engaging in body image-related cognitive fusion can trigger emotional and behavioral responses that are regulated by internal, body-focused events, leading to a disregard of other important cues such as external experiences and individual life values. The CFQ-BI can be administered online or in-person and is free to use. This chapter first discusses the development of the CFQ-BI and then provides evidence of its psychometrics. More specifically, the CFQ-BI is unidimensional per exploratory and confirmatory factor analyses and invariant across gender and sample type (clinical, nonclinical samples). Internal consistency reliability, test-retest reliability, convergent validity, discriminant validity, and incremental validity support its use. Next, this chapter provides the CFQ-BI items in their entirety, instructions for administration and scoring, and the item response scale. Links to known translations are included. Logistics of use, such as permissions, copyright, and contact information, are available for readers.