Among infants born at term, breastfeeding is associated with increased dietary variety in childhood. Preterm birth can limit early feeding options while simultaneously increasing risk for negative health outcomes that could benefit from dietary-based preventative measures. We assessed whether breastfeeding is associated with increased dietary variety at 1–3 years amongst children born preterm. We analyzed baseline data from two clinical trials investigating cognitive development after fatty-acid supplementation for 10-39 month-old children born before 35 weeks gestation (n = 189). At baseline, mothers reported breastfeeding history and completed a 161-item food-frequency questionnaire for their child. Dietary variety was assessed via 3 measures: (1) proportion items consumed at least once per month, (2) servings of a given item consumed relative to total monthly food servings, (3) daily probability of consuming a given item. Overall, 88% of children were ever breastfed (median duration = 89 days, range = 0–539), and 48% of children were ever exclusively breastfed (median duration = 59 days, range = 3–240). Exclusive breastfeeding duration was associated with dietary variety increases of 0.9% (95% CI = 0.1–1.7) for vegetables, 1.6% (95% CI = 0.2–3.0) for meat/fish, and 1.3% (95% CI = 0.2–2.4) for grain/starch, for each additional month of exclusive breastfeeding after adjustment for key confounders. Correspondingly, the variety of sweets consumed decreased by 1.2% (CI: −2.1, −0.3) per month of any breastfeeding after adjustment. These results are consistent with those in children born at term, and if causal, could provide additional support for exclusive breastfeeding to improve diet and health in children born preterm.