Cooperation among neighbouring countries is critical for managing security threats like terrorism and migration. Despite their proximity, states often struggle to cooperate for various reasons, including a lack of solidarity, which can harm regional peace and stability. This study uses qualitative research to examine West African nations’ cooperation in combating Islamist terrorism and aiding affected individuals across borders. Applying regional security complex theory and transnationalism, we assess how terrorism-driven migration impacts regional security, peace and development, highlighting cooperation challenges. This study redefines ‘neighbour’ in international relations, emphasising proactive international solidarity and shared responsibility to address insecurity.