Nanozymes are artificial enzymes that mimic natural enzyme-like activities and show great promise for tumor catalytic therapy. However, new nanozymes with multiple catalytic activities for multifunctional nanotheranostic use remain challenging to design. Herein, for the first time, iron phthalocyanine (Fe(II)Pc) was assembled with poly(l-lactide-co-glycolide)-block-poly(ethylene glycol) to prepare an Fe(II)Pc assembly (denoted as Fe(II)Pc-A). The obtained Fe(II)Pc-A could be applied as a smart near-infrared (NIR) light-responsive nanotheranostic for simultaneous photoacoustic imaging-guided photothermal therapy. Notably, Fe(II)Pc-A possessed peroxidase, catalase, and oxidase mimicking activities, which could not only catalyze the conversion of intratumoral H2O2 to •OH, but also degrade H2O2 to generate O2 and continuously catalyze the conversion of O2 to cytotoxic O2•-. Impressively, the dual reactive oxygen species (ROS) generation of Fe(II)Pc-A was further remarkably enhanced by the endogenous acidity of the tumor microenvironment and the exogenous NIR light-responsive photothermal effect. Moreover, the O2 self-supplying ability of Fe(II)Pc-A led to increased generation of O2•- for enhancing catalytic therapy in hypoxic tumor. These collective properties of Fe(II)Pc-A nanozyme enabled it to be a dual ROS generation accelerator for photothermally enhanced tumor catalytic therapy. Thus, a new type of high-performance nanozyme for multifunctional nanotheranostic use toward cancer was presented.