The evidence on the relationship between diet diversity in early life and allergic outcomes was few and inconsistent. We sought to determine the association of food diversity in the first year of life with allergic outcomes in the second year. Two thousand two hundred fifty-one mother-infant pairs from Tongji Maternal and Child Health Cohort (TMCHC) were involved in the study. Information on complementary foods introduction was obtained by telephone interview at 6- and 12-month postpartum follow-up. Any doctor-diagnosed allergic diseases in the second year were recorded at 2-year postpartum follow-up. Food allergies in infancy were assessed and self-reported by mothers at each postpartum follow-up. Multivariable logistic regression was used to examine the effect of food diversity at 6 and 12months of age on later allergic diseases and food allergy. A total of 135 (6.0%) infants reported allergic diseases at between 1 and 2years of age. Independent of food allergy history of infants and other potential confounders, less food diversity at 6months of age was associated with increased risk of later allergic diseases (OR 2.17, 95% CI 1.04-4.50 for 0 vs. 3-6 food groups). By 12months of age, significant inverse associations with later allergic diseases (OR 2.35, 95% CI 1.03-5.32 for 1-5 vs. 8-11 food groups, and OR 1.98, 95% CI 1.16-3.37 for 6-7 vs. 8-11 food groups) and food allergy (OR 2.10, 95% CI 1.29-3.42 for 1-5 vs. 8-11 food groups) were observed. Children with higher food diversity in both periods had the lowest risk of allergic diseases during the second year of life. A more diverse diet within the first year of life was associated with reduced risk of allergic diseases at 1-2years of age. Introducing higher diversity of foods from 6 to 12months of age might be an effective strategy to improve the allergy outcomes of infants in later life.