Water-soluble colloidal semiconductor quantum dots (QDs) as a new class of fluorescent probes with excellent optical properties have attracted considerable attention in bioapplications. Because of the large surface-to-volume ratio of QDs, especially in the case of QDs passivated with organic ligands, the photoluminescence (PL) of QDs is sensitive to the environmental conditions. Generally, the PL behavior of intracellular QDs is more complicated than that in solutions due to the complex cellular environment. In this review, the environmental influence on the PL behavior of intracellular thiol-capped CdTe QDs, such as the time-dependent spectral blueshift, photobleaching and lifetime shortening, is introduced and its mechanisms are discussed.