A novel dual-coreactants electrochemiluminescent (ECL) immunosensor based on CdS-MoS2 nanocomposites was designed for detection of procalcitonin (PCT). The CdS-MoS2 nanocomposites were synthesized through a simple one-pot hydrothermal method, and served as highly efficient luminescent material for the ECL immunosensor. In addition, we used H2O2 and K2S2O8 as dual-coreactants, generating stronger ECL emission than that of K2S2O8 or H2O2 as an individual coreactant, which could improve sensitivity of the immunosensor. Under optimum conditions, the ECL assay for PCT detection was developed with excellent sensitivity of a concentration variation from 0.0001 to 10 ng mL(-1) and limit of detection down to 33 fg mL(-1)(RSD = 0.10). Additionally, the proposed immunosensor showed high specificity, good reproducibility, and long-term stability. (C) The Author(s) 2018. Published by ECS.