Objectives - To determine the effect of a dietary intervention and micronutrient supplementation on self-reported infections in older adults. Design - A randomized, placebo-controlled intervention trial. Setting - Community living older people in South Yorkshire, United Kingdom. Participants - Two-hundred seventeen older adults aged 65 to 85. Intervention - Participants were randomized to a dietary intervention, a daily micronutrient supplement, or placebo for 3 months, with a 3-month follow-up. Measurements - Self-reported measures of infection were reported over the 6-month study period. Secondary outcome measures were nutritional status, dietary intake, quality of life, and depression. Results - Self-reported measures of infection over the 6-month duration of the study were significantly different between the treatment groups. The number of weeks in which illness affected life and the number of general practitioner and hospital visits were significantly lower in the food and micronutrient groups than in the placebo group. The number of weeks in which symptoms of an infection were described was significantly lower in the food group than the placebo and micronutrient groups. Significant improvements in biomarkers of micronutrient status were achieved in the food and micronutrient groups and showed significantly greater change than observed in the placebo group. Significant improvement in dietary intakes was observed in the food group only. Conclusion - Improving dietary intake and micronutrient status reduces the clinical impact of self-reported infections in older adults.