We present a new synthetic strategy to produce Gd(III)-decorated gold nanoparticles (AuNPs) for potential use as bimodal contrast agents (CA) for computed X-ray tomography (CT) and magnetic resonance imaging (MRI). The hybrid AuNPs exhibit high molar relaxivities (>12 000 mM⁻¹ s⁻¹ per particle), indicative of highly efficient CT/MRI CAs.