There is a need of expanding research on neonatal behaviour to encompass diverse global populations. However, few measures appropriate for use from birth in diverse cultural contexts exist. We present data from rural Gambia and the UK using the Neonatal Behavioural Assessment Scale (NBAS). In Phase 1, the scale was piloted for use in The Gambia, highlighting great utility for use in this setting. Adaptations included 1) additional explanation of some items to caregivers and 2) omission of items where the home environment necessitated to do so. In Phase 2, the NBAS was administered in both the UK and The Gambia. Item level comparisons across the sites showed fewer state changes in Gambian infants and a greater degree of examiner facilitation throughout the session. Factor analysis within the larger Gambian cohort indicated best model fits where first-order factors mapping onto each NBAS subscale were accompanied by a second-order 'Self-Organising System'-factor, mirroring prior factor analytic studies on the scale. Further, the habituation subscale had to be omitted from analyses due to large amounts missing data, highlighting potential differences across subscales when implementing the NBAS across diverse settings. We found associations between our NBAS factor scores and NBAS supplementary items. Examining known risk factors for early neonatal development, we found associations of the Social Interactive and Self-Organising System factor with pregnancy anxiety and gestational age at birth and birthweight, but not maternal anaemia. Our findings inform future studies seeking to understand the interplay between cultural contexts, perinatal factors, and early neurobehavioural development.