Background The Democratic Republic of Congo (DRC) has experienced political unrest, civil insecurity, and military disputes, resulting in extreme poverty and a severely impaired health care system. To reduce the morbidity and mortality in women and children by strengthening healthcare, this study aimed at exploring the relationship between self-reported insecurity of mothers and maternal health-seeking behaviours and diseases in children in the DRC. Method Data collected from 8144 mothers and 14,403 children from the Multiple Indicators Cluster Survey (MICS) conducted by the National Institute of Statistics in 2017–2018, in collaboration with the United Nations Children’s Fund (UNICEF), was used. The severity of the conflict in different provinces was measured using the Uppsala Conflict Data Program (UCDP) reports. Multivariate logistic regression and stratified analysis were utilized to explore the association between conflicts with maternal health-seeking behaviours and diseases among children. Results High self-reported insecurity was positively associated with skilled antenatal care (OR1.93, 95%CI 1.50–2.49), skilled attendants at delivery (OR1.42, 95%CI 1.08–1.87), and early initiation of breastfeeding (OR1.32, 95%CI 1.04–1.68). These associations were more significant in regions with more armed conflict. It was also found that children of mothers with high self-reported insecurity were more likely to suffer from diarrhoea (OR1.47, 95%CI: 1.14–1.88), fever (OR1.23, 95%CI 1.01–1.50), cough (OR1.45, 95%CI 1.19–1.77), and dyspnea (OR2.04, 95%CI 1.52–2.73), than children of mothers with low self-reported insecurity. Conclusions Conflicts increases mothers’ insecurities and negatively affects children’s development. However, high conflict regions have to increase governmental and international assistance to promote the availability and access to maternal and child health services.