Landfill mining, a systematic approach to deal with legacy waste, involves its excavation and processing to recover secondary resources and repurpose land. The present study explores the characteristics and valorization potential of landfill-mined fine fraction (LMFF) from dump sites in Boragaon, Ghazipur, Bhalswa, and Bandhwari, focusing on its composition, environmental risks, and reuse opportunities. Physico-chemical characterization reveals LMFF contains high-organic matter (13–17%), essential macro-nutrients, and a favorable C/N ratio, indicating its maturity and advanced decomposition. Nutrient levels mostly align with compost standards, suggesting potential use as a soil conditioner, but elevated heavy metal concentrations, exceeding permissible limits, pose significant environmental challenges. Total heavy metal analysis shows LMFF contains high levels of Zn, Cu, Pb, and Ni, with varying bioavailability and leachability across sites. Pollution indices highlight LMFF from Boragaon and Ghazipur to pose high potential ecological risk, and Bhalswa and Bandhwari considerable ecological risk necessitating its treatment to mitigate pollution risks. Various instrumental analyses confirm the presence of significant organic and inorganic matter, with morphological heterogeneity. Considering the evident ability of LMFF to cause contamination, appropriate treatment and mitigation strategies to stabilize heavy metals and enhance its reuse in civil engineering applications have been suggested.