Folic acid (FA)-targeted indocyanine green (ICG)-loaded nanoparticles (NPs) (FA-INPs) were developed to a near-infrared (NIR) fluorescence theranostic nanoprobe for targeted imaging and photothermal therapy of cancer. The FA-INPs with good monodispersity exhibited excellent size and fluorescence stability, preferable temperature response under laser irradiation, and specific molecular targeting to MCF-7 cells with FA receptor overexpression, compared to free ICG. The FA-INPs enabled NIR fluorescence imaging to in situ monitor the tumor accumulation of the ICG. The cell survival rate assays in vitro and photothermal therapy treatments in vivo indicated that FA-INPs could efficiently targeted and suppressed MCF-7 cells and xenograft tumors. Hence, the FA-INPs are notable theranostic NPs for imaging-guided cancer therapy in clinical application.