A novel, solution-based route to biocompatible, cysteine-capped gold–zinc telluride (Au–ZnTe) core–shell nanoparticles with potential in biomedical applications is described. The optical properties of the core–shell nanoparticles show combined beneficial features of the individual parent components. The tunable emission properties of the semiconductor shell render the system useful for imaging and biological labeling applications. Powder X-ray diffraction analysis reveals the particles contain crystalline Au and ZnTe. Transmission electron microscope (TEM) imaging of the particles indicates they are largely spherical with sizes in the order of 2–10 nm. Elemental mapping using X-ray energy dispersive spectroscopy (XEDS) in the scanning transmission electron microscope (STEM) mode supports a core–shell morphology. The biocompatibility and cytotoxicity of the core–shells was investigated on a human pancreas adenocarcinoma (PL45) cell line using the WST-1 cell viability assay. The results showed that the core–shells had no adverse effects on the PL45 cellular proliferation or morphology. TEM imaging of PL45 cell cross sections confirmed the cellular uptake and isolation of the core–shell nanoparticles within the cytoplasm via membrane interactions. The fluorescence properties of the Au–ZnTe core–shell structures within the PL45 cell lines results confirmed their bio-imaging potential. The importance and novelty of this research lies in the combination of gold and zinc telluride used to produce a water soluble, biocompatible nanomaterial which may be exploited for drug delivery applications within the domain of oncology.