AbstractThis study focuses on the development of environmentally friendly Au‐Cu2−xS/CuInS2 heteronanotrimers. The chosen strategy relies on the laser photodeposition of a single gold nanodot (ND) onto Janus Cu2−xS/CuInS2 heteronanocrystals (HNCs). This method offers precise control over the number, location, and size (5 to 8 nm) of the Au NDs by adjusting laser power for the career production, concentration of hole scavenger for charge equilibration in redox reactions, and gold precursor concentration, and exposure time for the final ND size. The photoreduction of gold ions onto HNCs starts systematically at the Cu2−xS tip. The Au deposition then depends on the CuInS2 segment length. For short HNCs, stable Au‐Cu2−xS/CuInS2 heteronanotrimers form, while long HNCs undergo a secondary photo‐induced step: the initial Au ND is progressively oxidized, with concomitant deposition of a second gold ND on the CuInS2 side, to yield Au2S‐Cu2−xS/CuInS2‐Au heteronanotrimers. Results are rationalized by quantitative comparison with a model that describes the growth kinetics of NDs and Au‐Cu2−xS transformation and emphasizes the importance of charge separation in predicting selective deposition in heteronanotrimer production. The key parameter controlling Au‐Cu2‒xS/CuInS2 HNCs is the photoinduced electric field gradient generated by charge separation, which is tailored by controlling the CuInS2 segment size.