To develop and validate an instrument to assess environmentally conscious eating (Green Eating [GE]) behavior (BEH) and GE Transtheoretical Model constructs including Stage of Change (SOC), Decisional Balance (DB), and Self-efficacy (SE).Cross-sectional instrument development survey.Convenience sample (n = 954) of 18- to 24-year-old college students from a northeastern university.The sample was randomly split: (N 1 ) and (N 2 ). N 1 was used for exploratory factor analyses using principal components analyses; N 2 was used for confirmatory analyses (structural modeling) and reliability analyses (coefficient α). The full sample was used for measurement invariance (multi-group confirmatory analyses) and convergent validity (BEH) and known group validation (DB and SE) by SOC using analysis of variance.Reliable (α > .7), psychometrically sound, and stable measures included 2 correlated 5-item DB subscales (Pros and Cons), 2 correlated SE subscales (school [5 items] and home [3 items]), and a single 6-item BEH scale. Most students (66%) were in Precontemplation and Contemplation SOC. Behavior, DB, and SE scales differed significantly by SOC (P < .001) with moderate to large effect sizes, as predicted by the Transtheoretical Model, which supported the validity of these measures.Successful development and preliminary validation of this 25-item GE instrument provides a basis for assessment as well as development of tailored interventions for college students.