Rapid clearance of nanoagents is a critical criterion for their clinical translation. Herein, it is reported that biodegradable and renal clearable nanoparticles are potentially useful for image-guided photothermal therapy of tumors. The multifunctional nanoparticles with excellent colloidal stability are synthesized through coordination reactions between Fe3+ ions and gallic acid (GA)/polyvinyl pyrrolidone (PVP) in aqueous solution. Detailed characterization reveals that the resulting Fe3+ /GA/PVP complex nanoparticles (FGPNs) integrate strong near-infrared absorption with paramagnetism well. As a result, the FGPNs present outstanding performance for photoacoustic imaging and magnetic resonance imaging of tumors, and outstanding photothermal ablation effect for tumor therapy owing to their high photothermal conversion efficiency. More importantly, the pharmacokinetic behaviors of the FGPNs determined through 125 I labeling suggest that the FGPNs are readily degraded in vivo showing a short biological half-life, and the decomposition products are excreted through either renal clearance pathway or bowel elimination pathway via stomach, which highlights the characteristics of the current multifunctional theranostic agent and their potential in clinical translation.