<p>This study aimed to evaluate the psychometric properties of the Dietarian Identity Questionnaire (DIQ), an instrument based on the Unified Model of Vegetarian Identity (UMVI), within a Brazilian context of adult vegetarians, dietary vegans and omnivores. Vegetarianism encompasses various dietary patterns that range from avoiding and reducing to excluding animal-derived foods, as is the case with dietary vegans. The UMVI conceptualizes vegetarianism and related dietary patterns as dietarian identities. Dietarian identity represents a novel framework within the Brazilian context, underscoring the significance of the present study. After transcultural adaptation, a Brazilian sample was recruited in two stages (<i>n</i> = 1181 and <i>n</i> = 226), comprising omnivores, vegetarians, and dietary vegans, aged 18 to 60 years. Data was collected via the RedCap platform, with participants being reached through vegetarian/dietary vegan groups in social media and direct outreach to various vegetarian associations. Psychometric evaluation included confirmatory factor analysis, assessment of convergent validity, and test-retest reliability. Additionally, multiple ANOVAs were conducted to explore differences among omnivores, vegetarians, and dietary vegans in the Brazilian population. The confirmatory factor analysis confirmed the instrument's internal structure and validity, with test-retest reliability and convergent validity further supporting its psychometric properties. Brazilian omnivores exhibited higher levels of Centrality, Personal Regard, Strictness, and Prosocial and Moral Motivations compared to data from other cultural contexts, such as Europeans and North Americans. These findings highlight unique aspects of Brazilian dietarian identity, challenging existing literature and emphasizing the need for further exploration of cultural influences on dietarian identity, including regional and cross-cultural perspectives.</p>