Aim: The aim of the study was to examine prospective associations of sleep characteristics (duration, timing, quality) with dietary and anthropometric measures among toddlers born preterm (<35 weeks). Methods: Children participated in the Omega Tots trial at 10–17 months' corrected age (Ohio, USA; 26 April 2012 to 6 April 2017). Caregivers reported toddlers' sleep at baseline using the Brief Infant Sleep Questionnaire. After 180 days, caregivers reported toddlers' past month diet in a food frequency questionnaire, and anthropometry was measured using standardised protocols. The toddler diet quality index (TDQI: higher scores indicating better quality), and weight‐for‐length, triceps skinfold and subscapular skinfold z‐scores were calculated. Linear and logistic regression assessed adjusted associations with dietary and anthropometric outcomes at 180‐day follow‐up (n = 284), and linear mixed models assessed changes in anthropometry. Results: Daytime sleep was associated with lower TDQI (βadj per hour = −1.62 (95% CI: −2.71, −0.52)) whereas night‐time sleep was associated with higher TDQI (βadj = 1.01 (95% CI: 0.16, 1.85)). Night‐time awakenings and caregiver‐reported sleep problems were also associated with lower TDQI. Night awakening duration and sleep‐onset latency were associated with higher triceps skinfold z‐score. Conclusion: Daytime and night‐time caregiver‐reported sleep showed opposite associations with diet quality, suggesting that sleep timing may be important. [ABSTRACT FROM AUTHOR]