In this work, Au@Cu₂O core–shell nanoparticles (NPs) were synthesized by simple solution route and applied for CO sensing applications. Au@Cu₂O core–shell NPs were formed by the deposition of 30–60 nm Cu₂O shell layer on Au nanorods (NRs) having 10–15 nm width and 40–60 nm length. The morphology of Au@Cu₂O core–shell NPs was tuned from brick to spherical shape by tuning the pH of the solution. In the absence of Au NRs, cubelike Cu₂O NPs having ∼200 nm diameters were formed. The sensor having Au@Cu₂O core–shell layer exhibited higher CO sensitivity compared to bare Cu₂O NPs layer. Tuning of morphology of Au@Cu₂O core–shell NPs from brick to spherical shape significantly lowered the air resistance. Transition from p- to n-type response was observed for all devices below 150 °C. It was demonstrated that performance of sensor depends not only on the electronic sensitization of Au NRs but also on the morphology of the Au@Cu₂O core–shell NPs.