Designing highly biocompatible organic semiconducting conjugated polymer dots (Pdots) with bright fluorescence and superior absorption properties in the second near-infrared window (NIR-II: 1000-1700 nm) remains a huge challenge for tumor phototheranostics. In this study, we constructed 4T1 cell membrane-coated m-PBTQ4F Pdots (CPdots) with enhanced NIR-II photoacoustic (PA) and fluorescence (FL) imaging capability for NIR-II photothermal therapy (PTT) of breast tumors. Our findings demonstrated that CPdots could specifically target breast tumors, leading to enhanced tumor accumulation after systemic administration in living mice. In addition, CPdots can not only serve as contrast agents for NIR-II PA and FL imaging for improved breast tumor detection but also generate more cytotoxic heat to improve PTT efficacy. Therefore, this pilot study opens an option avenue for developing new NIR-II Pdots with homologous targeting capability for enhanced phototheranostics of breast tumors.