This paper describes the first electromagnetic characterization of a self-biased circulator in molded interconnect device (MID) technology. The circulator was designed using a 3D full-wave commercial simulator. It consists of microstrip access lines connected to a Y-junction in Substrate Integrated Waveguide (SIW) technology. Unlike classical technologies, the SIW Y-junction was not fabricated using metallic vias but by a Laser Direct Structuring (LDS) technique. A molded Cyclo-Olefin Polymer (COP) was used as a substrate and 3D metallized. The microwave properties of LDS-compatible COP are not well known so we investigated them through the use of cavity-perturbation and rectangular waveguide characterization methods. The device was then machined to insert a pre-oriented strontium hexaferrite puck doped with cobalt and lanthanum (Sr0,7La0,3Fe11,7Co0,3O19). The characteristics of the MID circulator were assessed between 28 and 32GHz. Without magnets, insertion losses of 3.32dB were measured at 30.7GHz. At the same frequency, an isolation level of 13.89dB and return losses of 19.89dB were observed. These measurements demonstrate for the first time the high potential of MID technology for the realization of low-cost non-reciprocal devices. •Molded Interconnect Device technology was used to realize a self-biased circulator.•This is the first demonstration of a non-reciprocal effect in MID technology.•Pre-oriented hexaferrites enable a self-biased circulation.•(La,Co)0.3-SrM hexaferrite cylinder shows a remanence to saturation ratio of 90%.•The measured self-biased circulator shows insertion losses of 3.3 dB and an isolation level of 13.9dB at 30.7GHz.