This paper analyzes the presence of the New Christian minority within the system of curial agencies, a key structure for the interests of the Catholic monarchy in Rome. It was a stable network of agents that reflected the multiplicity of territories under the sovereignty of the Spanish Habsburgs and worked alongside the Spanish embassy to the Holy See. Factors explaining the significant converso presence and the curial dynamics behind the creation of the system of agencies are examined, illustrating the operation thereof through various case studies, with special attention to Portugal’s agency. A transversal approach is employed in the study of this system, which has been very poorly understood until now.