<p>Catalysts play a central role in syngas conversion technology, and improving their performance continues to attract considerable research interest. The nature of the nitrogen precursor can strongly influence the doping configuration, defect structure, and surface properties of N-doped graphene; however, how these variations govern the dispersion of cobalt nanoparticles and the resulting Fischer-Tropsch synthesis performance remains poorly understood. In this work, four chemically distinct nitrogen-bearing compounds (histidine, ammonia solution, hydrazine hydrate, and urea) were employed as nitrogen sources to prepare N-doped graphene-supported cobalt catalysts via a hydrothermal route, and their effects on the physicochemical properties of the supports and on FTS behavior were systematically investigated. Among the precursors examined, urea yielded the most favorable support. The combination of preserved structural integrity, a large specific surface area, and a moderate, defect-rich degree of N-doping provided abundant anchoring sites that promoted the uniform dispersion of cobalt nanoparticles with moderate crystallite sizes. As a result, the urea-derived catalyst achieved the highest CO conversion and the largest cobalt-time yield (CTY) among all samples, together with a favorable C₅₊ selectivity of approximately 78%, indicating a genuine enhancement of the intrinsic activity of the cobalt phase rather than a purely apparent effect. Moreover, all catalysts exhibited low CO₂ selectivity, confirming that the graphene-based support effectively suppresses the undesired water–gas shift activity. This precursor comparison provides a practical guideline linking the selection of nitrogen source to support structure, cobalt dispersion, and FTS performance.</p>