A 2,6-dibrominated 3,5-distyryl boron-dipyrromethene (BODIPY) dye with a moderately high singlet oxygen quantum yield was encapsulated in Pluronic ® F-127 micelles, and its dark cytotoxicity and photodynamic activity were investigated on the human breast adenocarcinoma MCF-7 cell line. The BODIPY dye exhibited very low dark toxicity and a significant PDT effect when added in drug formulations consisting of 5.0% (v/v) DMSO in supplemented Dulbecco’s modified Eagle’s medium (DMEM) and as Pluronic ® F-127 micelle encapsulation complexes in supplemented DMEM alone. An IC 50 value of 4 ± 2 μM was obtained when the BODIPY dye was encapsulated in Pluronic ® F-127 micelles during in vitro photodynamic activity studies in MCF-7 cancer cells with a 660 nm light emitting diode.