A new class of near-infrared-II (NIR-II) photothermal and photoacoustic agents, nanographene-porphyrin hybrids (NGP-1 and NGP-2), has been developed for cancer theranostics. These agents, composed of porphyrins fused with nanographene units, exhibit strong absorption in the NIR-I (up to ~1000 nm) and NIR-II (up to ~1400 nm) regions. When encapsulated in self-assembled nanoparticles (NPs), NGP-1 and NGP-2 demonstrate high photothermal conversion efficiencies of 60% and 69%, respectively, under 808 and 1064 nm laser irradiation. NGP-2-NPs show excellent photostability, biocompatibility, and photoacoustic properties, enabling in vivo photothermal therapy (PTT) and photoacoustic imaging (PAI) in the NIR-II window. In vitro and in vivo studies reveal that NGP-2-NPs effectively target and destroy cancer cells, with no significant toxicity. In vivo experiments on 4T1 tumor-bearing mice show that NGP-2-NPs can accumulate in tumors and induce significant temperature increases, leading to complete tumor elimination. The agents also demonstrate good biocompatibility, with no significant adverse effects on major organs. This study highlights the potential of NGP-2-NPs for NIR-II-based cancer theranostics and suggests their application in other bioimaging and therapeutic areas. The results demonstrate the effectiveness of NGP-2-NPs in NIR-II PTT and PAI, offering a promising platform for cancer treatment.A new class of near-infrared-II (NIR-II) photothermal and photoacoustic agents, nanographene-porphyrin hybrids (NGP-1 and NGP-2), has been developed for cancer theranostics. These agents, composed of porphyrins fused with nanographene units, exhibit strong absorption in the NIR-I (up to ~1000 nm) and NIR-II (up to ~1400 nm) regions. When encapsulated in self-assembled nanoparticles (NPs), NGP-1 and NGP-2 demonstrate high photothermal conversion efficiencies of 60% and 69%, respectively, under 808 and 1064 nm laser irradiation. NGP-2-NPs show excellent photostability, biocompatibility, and photoacoustic properties, enabling in vivo photothermal therapy (PTT) and photoacoustic imaging (PAI) in the NIR-II window. In vitro and in vivo studies reveal that NGP-2-NPs effectively target and destroy cancer cells, with no significant toxicity. In vivo experiments on 4T1 tumor-bearing mice show that NGP-2-NPs can accumulate in tumors and induce significant temperature increases, leading to complete tumor elimination. The agents also demonstrate good biocompatibility, with no significant adverse effects on major organs. This study highlights the potential of NGP-2-NPs for NIR-II-based cancer theranostics and suggests their application in other bioimaging and therapeutic areas. The results demonstrate the effectiveness of NGP-2-NPs in NIR-II PTT and PAI, offering a promising platform for cancer treatment.