Our primary objective was to assess if sustained participation in continuous quality improvement (CQI) activities could improve delivery of € basic developmental care' to disadvantaged children in primary care settings. Secondary objectives were to assess if delivery of developmental care differed by age and geographic location.Data were analysed using multivariable logistic regression and generalised estimating equations. 109 indigenous primary care centres across Australia from 2012 to 2014 and2466 client files from indigenous children aged 3-59 months were included. Outcome measures were delivery of basic developmental care.We found that the proportion of children who received basic developmental care ranged from 55% (advice about physical and mental stimulation of child) (1279, 55.1%) to 74% (assessment of developmental milestones) (1510, 73.7%). Ninety-three per cent (92.6%, 88) of children received follow-up care. Centres with sustained CQI participation (completed three or more consecutive audit cycles) (508, 53.9%) were twofold more likely to deliver basic developmental care compared with centres without sustained CQI (completed less than three consecutive audit cycles) (118, 31.0%) (adjusted OR (aOR) 2.37, 95% CI 1.33 to 4.23). Children aged 3-11 months (229, 54.9%) were more likely to receive basic developmental care than children aged 24-59 months (151, 38.5%) (aOR 2.42, 95% CI 1.67 to 3.51). Geographic location had little effect (aOR 0.68, 95% CI 0.30 to 1.53). Overall our study found that sustained CQI can improve basic developmental care in primary care settings. However, many disadvantaged children are not receiving services. Improved resourcing of developmental care and CQI in primary care centres is needed.