Background: Extreme prematurity or extremely low birth weight (ELBW) can adversely affect behaviour. Nondisabled ELBW children are at risk of behavioural problems, which may become a particular concern after commencement of formal education. This study explored the frequency of behavioural and emotional problems amongst nondisabled ELBW children at 4 to 5 years of age and whether intervention had a positive influence on behaviour. The relationship between behaviour, gender, and other areas of performance at 5 years was explored. Methods: Fifty 4-year-old children (born <28 weeks gestation or birth weight <1,000 g) with minimal/mild motor impairment were randomly allocated to intervention (n = 24) or standard care (n = 26). Intervention was 6 group-based physiotherapy weekly sessions and home programme. Standard care was best practice advice. The Child Behavior Checklist (CBCL) for preschool children was completed at baseline and at 1-year post-baseline. Other measures at follow-up included Movement Assessment Battery for Children Second Edition, Beery Visual-Motor Integration Test 5th Edition, and Peabody Picture Vocabulary Test 4th Edition. Results: The whole cohort improved on CBCL total problems score between baseline (mean 50.0, SD 11.1) and 1-year follow-up (mean 45.2, SD 10.3), p = .004. There were no significant differences between groups over time on CBCL internalizing, externalizing, or total problems scores. The intervention group showed a mean difference in total problems score of −3.8 (CI [1.5, 9.1]) between times, with standard care group values being −4.4 (CI [1.6, 7.1]). Males had higher total problems scores than females (p = .026), although still performed within the “normal” range. CBCL scores did not correlate with other scores. Conclusions: The behaviour of nondisabled ELBW children was within the “normal” range at 4 to 5 years, and both intervention and standard care may have contributed to improved behavioural outcomes. Behaviour was not related to performance in other developmental domains.