This study assessed the ecological validity of the Yale Food Addiction Scale (YFAS 2.0) with ecological momentary assessment (EMA) and explored the internal consistency and convergent validity of a momentary food addiction scale. Adults (N = 49) who met criteria for binge-eating disorder and/or food addiction (age = 34.9 ± 12.1 years; 77.1% cisgender female; 55.1% non-Hispanic White) completed online questionnaires and a 10-day EMA protocol. Analyses examined (a) associations between the YFAS 2.0 and EMA-measured variables corresponding to food addiction criteria, (b) reliability of a momentary food addiction scale (EMA-FA), and (c) concurrent associations between EMA-FA and EMA-measured negative affect, impulsivity, eating expectancies, body satisfaction, consumption of palatable food, and taste response to palatable food. YFAS scores were associated with EMA-reported variables corresponding to food addiction criteria (ps < .045). The multilevel reliability for EMA-FA was adequate (ω = .75-.94). Individuals with higher EMA-FA scores reported greater negative affect, impulsivity, appetite, palatable food consumption, taste response to palatable food, and contrary to expectations, greater body satisfaction (ps < .01). Within-person effects emerged for EMA-FA predicting higher negative affect, impulsivity, likelihood of palatable food consumption, more pleasurable taste responses after consuming palatable foods, yet lower body satisfaction, appetite, and eating expectancies (ps < .01). Results support the ecological validity of the YFAS 2.0, and additional evidence of convergent validity and internal consistency was demonstrated for a momentary food addiction scale. This assessment of the psychometric properties of the YFAS will ultimately further its utility and relevance in the study and diagnosis of food addiction. (PsycInfo Database Record (c) 2024 APA, all rights reserved).