Semiconductor quantum dots (QDs) have received significant attention as unique photoluminescent materials for biological imaging and sensing. Charge transfer (CT) modulation of QD emission has recently emerged as a promising detection modality in these applications; however, much still remains unknown about the mechanism through which an electron or hole transfers from a QD exciton to a redox active moiety in a bioconjugate construct. Here, we highlight the utility and challenges of CT for QD-based biosensing, particularly in comparison to Förster resonance energy transfer (FRET), and summarize the current understanding of this process, which is situated at the intersection between biological and photovoltaic research with QDs.