Background <p>This study examined the wealth-related inequality in women healthcare seeking behaviour for under-five children illness in Afghanistan and its determinants.</p> Methods <p>Data of 32409 mothers/caregivers of children under-five were extracted from Afghanistan Multiple Indicator Cluster Survey conducted in 2022. Wealth-related inequalities in women healthcare seeking behaviour for under-five children illness was investigated using Erreygers and Wagstaff concentration indices and curve. Contributions of selected factors to the total inequality were estimated using the Erreygers decomposition technique.</p> Results <p>The Erreygers and Wagstaff normalized concentration indices for women healthcare seeking behaviour for under-five children illness was 0.040; <i>p</i> &lt; 0.000 and 0.042; <i>p</i> &lt; 0.000 respectively. Hence, women healthcare seeking behaviour for children under-five illness was heavily concentrated among women from richer households and disfavoured women from poorer households. The decomposition findings revealed that household wealth (265%), residency in rural areas (-125%), access to mobile phone (-83%), access to internet (67%) and mothers’ education (26%) were the major determinants of pro-rich inequalities.</p> Conclusion <p>Policy makers, the private and development actors in Afghanistan should promote inclusive income generation interventions and healthcare awareness programmes, including women from poor households to eliminate wealth-related inequalities in women healthcare seeking behaviour. There is need for decentralizing health facilities in both rural and urban areas to improve equitable access to healthcare services. There is scope for disseminating health education through mobile phones and internet, reaching out to all areas to improve knowledge on children’s illnesses and subsequently reduce inequalities in women health seeking behaviours.</p>