Aim: To assess neurodevelopment and growth at 2 years corrected age in children born extremely preterm, supplemented with Limosilactobacillus reuteri or placebo. Methods: Design: Secondary analysis of register data after randomised double-blind placebo-controlled trial. Setting: Inclusion at two neonatal intensive care units in Sweden. Local follow-up per national guidelines. Subjects: 134 infants born at 23-27 weeks' gestation with a birth weight < 1000 g. Intervention: Daily enteral supplementation with placebo or Limosilactobacillus reuteri DSM 17938 (2.5 x 10(8) colony forming units), from within 72 h after birth to postmenstrual week 35-36. Main outcome measures: Bayley-III developmental assessment and auxology at 24 +/- 3 months corrected age. Results: Follow-up data were available for 110 of 117 surviving participants, and 85 children were assessed with Bayley-III. Mean language score after supplementation with L. reuteri was 90 (95% confidence interval: 85-95) compared to 83 in the placebo group (95% CI: 78-88), p = 0.04. No other significant differences in neurodevelopment or growth were observed. Conclusion: Supplementation with L. reuteri in extremely preterm infants was not associated with altered growth nor general neurodevelopmental outcomes at 2 years while language index was improved. This is interesting given previously reported early improved growth of head circumference.