Food mishandling is thought to be more acute among young adults; yet little is known about why they may engage in risky food handling behaviors. The purpose of this study was to create valid, reliable instruments for assessing key food safety psychosocial measures. Development of the measures began by examining published studies and behavior change theories to identify the psychosocial factors associated with personal health choices and 3 psychosocial factors were identified: beliefs, locus of control, and self-efficacy. Development of items for the belief questionnaire began by identifying the belief constructs that could provide insight into how food safety behavior change programs should be framed to evoke improved behaviors and drafting items. The locus of control questionnaire was modeled after the Health Locus of Control Questionnaire. Self-efficacy questionnaire development included defining self-efficacy, identifying environmental contexts affecting self-efficacy, and constructing an item pool. The questionnaires were pretested with young adults (n= 180) and refined. A pilot test (n= 77) was conducted to further refine the beliefs and self-efficacy questionnaires. Finally, young adults (n= 4343, mean age 19.9 [plus or minus] 1.7 SD y) from 21 universities and colleges across the country completed the questionnaires. Analysis of their responses revealed that these questionnaires met or exceeded standards indicative of high-quality psychosocial food safety measures. These questionnaires should be useful in generating baseline data from adults as well as establishing the value of these measures in assessing the effectiveness of food safety interventions.