Background <p>Infant sleep is considered a critical determinant of early neurodevelopment. Sleep patterns and habits vary across various socio-cultural contexts. However, few studies have explored the relationship between infant sleep patterns and developmental outcomes in non-Western populations. We aimed to investigate associations between sleep parameters and neurodevelopmental outcomes at 12 months of age in a sample of Iranian infants.</p> Methods <p>This study was conducted on 646 infants from the PERSIAN Birth Cohort in Isfahan, Iran. Sleep characteristics were assessed using the Brief Infant Sleep Questionnaire (BISQ), including nocturnal and daytime sleep duration, night waking frequency and duration, sleep onset time, and sleep latency. Neurodevelopmental outcomes were measured using the Ages and Stages Questionnaire (ASQ), covering five domains: communication, gross motor, fine motor, problem-solving, and personal-social development. Multivariable linear regression models were applied to examine the associations after adjusting for infant and maternal characteristics.</p> Results <p>Longer nocturnal sleep duration was significantly associated with higher personal-social development scores (β = 0.52, <i>p</i> = 0.03) and better communication scores (β = 0.42, <i>p</i> = 0.05). Increased night waking duration was negatively associated with both personal-social (β = –0.92, <i>p</i> &lt; 0.001) and total ASQ scores (β = –2.01, <i>p</i> = 0.004). More frequent night wakings were associated with lower problem-solving scores (β = –0.44, <i>p</i> = 0.008), and later sleep onset time was linked to reduced personal-social development (β = –0.59, <i>p</i> = 0.04).</p> Conclusion <p>Infant sleep duration and continuity are significantly related to social, cognitive, and communicative development. These findings underscore the need for culturally sensitive sleep interventions and routine sleep assessments in paediatric care.</p> Impact <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Infant sleep is considered a critical determinant of early neurodevelopment. Sleep habits vary across socio-cultural contexts.</p> </ItemContent> <ItemContent> <p>Infant sleep duration and continuity are significantly related to social, cognitive, and communicative development in a Middle Eastern setting.</p> </ItemContent> <ItemContent> <p>These findings underscore the need for culturally sensitive routine sleep assessments in paediatric care.</p> </ItemContent> </UnorderedList></p>