Objectives To understand the barriers to programme success among high‐needs families in KidsFirst, an early childhood intervention programme. Methods Using a qualitative approach, a secondary analysis was performed using the qualitative data set (111 interviews and focus groups with 242 participants) from the KidsFirst programme evaluation. Data analysis was conducted to identify common experiences among high‐needs families in the programme and barriers to programme success. Results Participants identified housing insecurity as a major factor impeding programme delivery, retention and successful outcomes. Housing insecurity was shown to create or exacerbate ongoing crises among high‐needs families. Only after housing insecurity was addressed were families able to benefit from the KidsFirst programme. Conclusions The findings of this research suggest that until baseline material security is established for high‐needs families, early childhood development (ECD) interventions will be limited in meeting their objectives. In order to have the most effect for those living in poverty, helping families to achieve basic material security, including secure housing, should precede the targeted provision of psychosocial ECD supports. This finding has implications for how ECD intervention programmes could more effectively be designed and whom they should target.