X-ray CT imaging can be complementary to fluorescence and photoacoustic imaging (FLI and PAI), allowing for high spatial resolution and high-sensitivity multimodal imaging for imaging guided treatment. In this study, the CT contrast agent iohexol was co-encapsulated with indocyanine green (ICG) within nanoliposomes (NLs) to explore their interaction and possible application of this liposomal formulation (LGI) in cancer theranostics. The photophysical properties of LGI were studied to assess the effect of iohexol on ICG that can enhance the efficiency of ICG-based near infrared photodynamic therapy (PDT). The CT, FLI and PA imaging abilities of LGI were also investigated. Furthermore, the near infrared phototherapy of cancer cells in vitro was performed, exhibiting higher phototherapy efficacy of LGI in comparison with other ICG formulations. We conclude that LGI can serve as a highly efficient theranostic nanoplatform for multimodal (fluorescence, CT and PA) imaging and near infrared phototherapy.