Studies showed that upgrading urban slums could bridge income inequality, create better opportunities, and mitigate/prevent virus spread in slums environment. There is a paucity of research concerning regenerating urban slums to achieve Goal 1 in Nigeria with reference to the post-COVID-19. Therefore, this research explored the impact of COVID-19 on slums in Nigerian cities and recommend measures to transform slums into sustainable cities and bridge income inequality to improve achieving Goal 1. The research used an interview type of qualitative research design and covered five major cities across Nigeria. The researchers engaged thirty interviewees (selected construction practitioners, NGOs, medical experts, and government agencies). The study adopted a thematic method to analyse the collated data. Findings show an increased poverty level across the five slum cities covered during and immediately after the pandemic. The significant impacts are high exposure to contagious and non-contagious infections, increased food insecurity, homelessness, unemployment, increased crime rates, and worse overcrowding during the lockdown. The study recommended measures to regenerate urban slums. The findings would stir policymakers to promote urban slum upgrading. Findings will support and provide insight into the active transformations of slums for the benefit of humanity and mitigate climate disruptions in future pandemics.