Noninvasive multimodality imaging-guided precision photothermal therapy (PTT) is proven to be an effective strategy for tumor theranostics by integrating diagnostics and therapeutics in one nanoplatform. In this study, indocyanine green (ICG)-conjugated and radionuclide iodine-125 (125 I)-labeled polymeric micelles (PEG-PTyr(125 I)-ICG PMs) are strategically prepared by the self-assembly of the ICG-decorated amphiphilic diblock polymer poly(ethylene glycol)-poly(l-tyrosine-125 I)-(indocyanine green) (PEG-PTyr(125 I)-ICG). The as-prepared polymeric micelles exhibit favorable biocompatibility, excellent size/photo/radiolabel stability, a high-photothermal conversion efficiency, a passive tumor-targeting ability, and a fluorescence (FL)/photoacoustic (PA)/single photon emission computed tomography (SPECT) imaging property. After tail intravenous injection, the polymeric micelles can efficiently accumulate at the tumor site and present comprehensive FL/PA/SPECT images with a high sensitivity, excellent spatial resolution, and unlimited tissue penetration under near-infrared (NIR) irradiation. Upon 808 nm laser irradiation, the subsequent precision PTT of tumors can be achieved with minimal cumulative side effects. Thus, this capable multifunctional nanoplatform with simple components and preparation procedures for FL/PA/SPECT multimodality imaging-guided PTT can be a potential candidate for clinical tumor theranostics.