Photothermal therapy is a promising strategy for treating tumors and bacterial infections by using light irradiation to locally heat tissues. Metalloisoporphyrinoid materials have been investigated for their use as singlet oxygen photosensitizers for photodynamic therapy but remain underexplored as photothermal agents. Recently, two metallophlorin and two metalloisocorrole materials were found to have strong near-infrared absorbance, with low photoluminescent quantum yields, suggesting high rates of nonradiative decay. Here we demonstrate that when encapsulated into aggregated organic nanoparticles (a-Odots), these materials show high photothermal conversion efficiencies between 67.3 ± 8.4 and 75.7 ± 4.1%. When considered alongside their ability to generate singlet oxygen, these materials may show promise as agents for dual photothermal and photodynamic therapy.