Interferon gamma (IFN-gamma) plays an important role in immune responses in a variety of infections and diseases. The measurement of IFN-gamma concentration can facilitate disease diagnosis. In this study, measurement of IFN-gamma concentration using a nanoparticle-based electrochemical immunosensor is reported. IFN-gamma was captured by antibody-functionalized magnetic nanoparticles (MNPs) and labeled with gold nanoparticles (AuNPs) conjugated with a second anti-IFN-gamma antibody and multiple cadmium sulfide nanoparticles (CdS-NPs), thus forming the MNP-IFN-gamma-Au-CdS complex. After magnetic separation, the complex was resuspended in a dilute nitric acid solution, mixed with bismuth, and added to a screen-printed carbon electrode (SPCE) chip. The electrochemical signal from the CdS-NPs was measured using square wave anodic stripping voltammetry (SWASV). Maximum current at -0.87 V was linearly associated with IFN-gamma concentration over the range of 0.01 to 1 IU/ml. Measurement of IFN-gamma concentration with this immunosensor required about 1 hour. These characteristics suggest that, with optimization, this immunosensor may have clinical utility. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: [email protected]. All rights reserved.