A disposable immunosensor for Salmonella enterica subsp. enterica serovar Typhimurium LT2 (S) detection using a magneto-immunoassay and gold nanoparticles (AuNPs) as label for electrochemical detection is developed. The immunosensor is based on the use of a screen-printed carbon electrode (SPCE) that incorporates a permanent magnet underneath. Salmonella containing samples (i.e. skimmed milk) have been tested by using anti-Salmonella magnetic beads (MBs-pSAb) as capture phase and sandwiching afterwards with AuNPs modified antibodies (sSAb-AuNPs) detected using differential pulse voltammetry (DPV). A detection limit of 143 cells mL−1 and a linear range from 103 to 106 cells mL−1 of Salmonella was obtained, with a coefficient of variation of about 2.4%. Recoveries of the sensor by spiking skimmed milk with different quantities of Salmonella of about 83 and 94% for 1.5×103 and 1.5×105 cells mL−1 were obtained, respectively. This AuNPs detection technology combined with magnetic field application reports a limit of detection lower than the conventional commercial method carried out for comparison purposes in skimmed milk samples.