Background <p>To describe the prevalence of overweight and obesity in adults living with type 1 diabetes and examine the association between biopsychosocial factors according to weight status.</p> Methods <p>A single-center, cross-sectional study was conducted in adults with type 1 diabetes attending a tertiary hospital between 2018 and 2020. Participants completed an online survey with validated questionnaires to assess physical activity; measure anxiety and depression; evaluate the perception of health-related quality of life [Spanish version of Diabetes Quality of Life Questionnaire (EsDQoL)], assess eating disorders [Spanish version of Diabetes Eating Problem Survey (EPAD-R)] and measure neuroticism. Sociodemographic data and information from the last outpatient visit regarding diabetes history, long-term complications, current insulin therapy, anthropometric measurements and laboratory data were also included.</p> Results <p>Data from 459 surveys were available for analysis. Participants had a mean (SD) of age of 44.7 (14.0) years; 55.6% were women; BMI 26.0 (4.7) kg/m² and the HbA_1c was 7.57%. The prevalence of overweight (BMI 25–29.9 kg/m²) and obesity (BMI &gt; 30 kg/m²) was 38.8% and 14.8%, respectively, with 10.6% being class I (30–34.9 kg/m²), 2.2% class II (35–39.9 kg/m²) and 2.0% class III (&gt;40 kg/m²). Older age, living with a child/children, a higher EPAD-R score, a higher total insulin doses, receiving lipid-lowering therapy, and a higher EsDQoL score in the <i>diabetes-related worries</i> dimension were associated with a greater likelihood of living with obesity.</p> Conclusions <p>Overweight and obesity are highly prevalent among adults living with type 1 diabetes, and the identified biopsychosocial factors reveals how excess weight arises from complex interactions among demographic, clinical, and psychological influences.</p> <p></p>