Background: Obesity is a major health concern in Cyprus and Greece, where mindful eating (ME) could aid in weight management by fostering awareness of eating behaviors. This cross-sectional study explores associations between ME, BMI, vitamin D levels, and sleep among 612 Cypriot and Greek adults (22.1% male, median age 33.5). Methods: Participants completed an online survey, including the Mindful Eating Questionnaire, over two phases (2022: N1 = 438; 2023: N2 = 174). Results: The mean ME score was 2.61 ± 0.36, with most participants classified as medium "mindful eaters." Significant negative correlations were observed between Awareness scores and BMI for Cypriots (r = -0.30, p = 0.01) and Greeks (r = -0.20, p = 0.05), while higher Disinhibition scores correlated positively with BMI (Cypriots: r = 0.35, p = 0.005; Greeks: r = 0.25, p = 0.02). Vitamin D was not tested in 63.8% of participants, and 57.5% did not take supplements, with seasonal variations (p = 0.043). Positive associations were also observed between vitamin D levels, ME scores, and sleep duration. Conclusions: These findings highlight the potential of mindful eating practices and vitamin D supplementation in obesity management. Public health interventions should consider promoting ME, routine vitamin D testing, and adequate sleep for comprehensive weight management.