Neurocognitive deficits in sickle cell disease (SCD) may impair adult care engagement. We investigated the relationship between neurocognitive functioning and socio-environmental factors with healthcare transition outcomes. Adolescents aged 15-18 years who had neurocognitive testing and completed a visit with an adult provider were included. Transition outcomes included transfer interval from paediatric to adult care and retention in adult care at 12 and 24 months. Eighty adolescents (59% male, 64% HbSS/HbSβ0 -thalassaemia) were included. Mean age at adult care transfer was 18·0 (±0·3) years and transfer interval was 2·0 (±2·3) months. Higher IQ (P = 0·02; PFDR = 0·05) and higher verbal comprehension (P = 0·008; PFDR = 0·024) were associated with <2 and <6 month transfer intervals respectively. Better performance on measures of attention was associated with higher adult care retention at 12 and 24 months (P = 0·009; PFDR = 0·05 and P = 0·04; PFDR = 0·12 respectively). Transfer intervals <6 months were associated with smaller households (P = 0·02; PFDR = 0·06) and households with fewer children (P = 0·02; PFDR = 0·06). Having a working parent was associated with less retention in adult care at 12 and 24 months (P = 0·01; P = 0·02 respectively). Lower IQ, verbal comprehension, attention difficulties and environmental factors may negatively impact transition outcomes. Neurocognitive function should be considered in transition planning for youth with SCD.