Organic/inorganic nanohybrids hold great importance in fabricating multifunctional theranostics to integrate therapeutic functions with real‐time imaging. Although Au nanorods (NRs) have been employed for theranostics, complicated design of materials limits their practical applications. In this work, new multifunctional theranostic agents are designed and synthesized employing Au NRs with desirable near‐infrared absorbance as the cores. A facile “grafting‐onto” approach is put forward to prepare the series of hierarchical nanohybrids (Au‐PGEA and Au‐PGED) of Au NRs and poly(glycidyl methacrylate)‐based polycations. The resultant nanohybrids can be utilized as gene carriers with high gene transfection performances. The structural effect of polycations on gene transfection is investigated in detail, and Au‐PGEA with abundant hydroxyl groups on the surface exhibits superior performance. Au‐PGEA nanohybrids are further validated to possess remarkable capability of combined photothermal therapy (PTT) and gene therapy (GT) for complementary tumor treatment. Moreover, significantly enhanced computed tomography (CT)/photoacoustic (PA) signals are detected both in vitro and in vivo, verifying the potential of Au‐PGEA for dual‐modal imaging with precise and accurate information. Therefore, these multifunctional nanohybrids fabricated from a simple and straightforward strategy are promising for in vivo dual‐modal CT/PA imaging guided GT/PTT therapy with high antitumor efficacy.