Background: Japan’s rapidly aging population has increased the urgency of addressing frailty among older adults. Oral hypofunction and malnutrition are recognized as key contributors to frailty, and both are considered reversible through early interventions. However, little is known about the effectiveness of integrating nutritional guidance and oral function training in community dental clinics. This study aimed to examine the association between dietary variety, oral function, and body composition among outpatients aged 50 years and older, and to evaluate the effects of targeted interventions over a 1-year period. Methods: A total of 74 outpatients (mean age 72.3±9.6 years) were assessed at baseline and after 1 year. Dietary variety was evaluated using the Dietary Variety Score (DVS), and oral function was assessed using seven standardized parameters. Body composition, including weight, body fat percentage, and muscle mass, was assessed using a bioelectrical impedance analyzer. Based on DVS results, registered dietitians provided nutritional counseling, while dental hygienists delivered tailored oral function training. Statistical analyses included the Wilcoxon signed-rank and McNemar’s tests. Results: Significant improvements were observed in eight of the ten DVS food groups, resulting in a higher total DVS score. Tongue coating index and tongue pressure also improved significantly, and the prevalence of oral hypofunction declined. No significant changes were found in body composition. Conclusion Integrating nutritional guidance and oral function training in a community dental setting improved dietary variety and oral function in older adults. These findings suggest that multidisciplinary care in community dental clinics may contribute to health promotion and frailty prevention.