© 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc. Antibody-based photodynamic therapy-photoimmunotherapy (PIT)-is an ideal modality to improve cancer treatment because of its selective and tumor-specific mode of therapy. Because the use of PIT for cancer treatment is continuing to be described, there is great need to characterize a standardized light source for PIT application. In this work, we designed and manufactured a light-emitting diode (LED)/PIT device and validated the technical feasibility, applicability, safety, and consistency of the system for cancer treatment. Methods: To outline the characteristics and photobiologic safety of the LED device, multiple optical measurements were performed in accordance with a photobiologic safety standard. A luciferase-transfected breast cancer cell line (2LMP-Luc) in combination with panitumumab- IRDye 700DX (pan-IR700) was used to validate the in vitro and in vivo performance of our LED device. Results: Testing revealed the light source to be safe, easy to use, and independent of illumination and power output (mWcm-2) variations over time. For in vitro studies, an LED dose (2, 4, 6 J cm-2)-dependent cytotoxicity was observed using propidium iodide exclusion and annexin V staining. Dosedependent blebbing was also observed during microscopic analysis. Bioluminescence signals of tumors treated with 0.3 mg of pan- IR700 and 50 J cm-2 decreased significantly (.80%) compared with signals of contralateral nontreated sites at 4 h and at 1 d after PIT. Conclusion: To our knowledge, a normalized and standardized LED device has not been explicitly described or developed. In this article, we introduce a standardized light source and validate its usability for PIT applications.