Abstract: The growing demand for Ni and Co in the new energy sector necessitates efficient extraction methods for limonitic laterite ores. This study demonstrated the effectiveness of sodium sulfate (Na₂SO₄) as an additive for enhancing the co-enrichment of Ni and Co during solid-state reduction. Na₂SO₄ promoted the formation of two distinct liquid phases, low-melting-point FeS–FeO–Fe and NaAlSiO₄–NaFeSiO₄, facilitating the migration and aggregation of Ni–Co–Fe alloy particles, leading to a high-grade alloy powder with 11.98wt% Ni and 0.88wt% Co and recoveries of 94.03% and 80.16%, respectively. Ni–Co–Fe particle growth was mainly driven by the FeS–FeO–Fe eutectic melt, aligned with a liquid-phase sintering mechanism. Pilot-scale rotary kiln experiments validated the industrial feasibility of this approach, which offers a promising solution for the sustainable extraction of these critical metals.