The fluorescence of 5-carboxytetramethylrhodamine (TMR) and fluoresceinisotkiocyanate (FITC) when bound to double-stranded DNA (dsDNA) residues (24 bp, 138 bp, and 1345 bp) was investigated by steady-state and time-resolved fluorescence measurements. The measurements were carried out using both single-labeled (FITC or TMR) and double-labeled dsDNA (FITC and TMR). A decrease in the fluorescence intensity and lifetime of TMR was observed when a FITC molecule was bound to the opposite end of the nucleic acid structure. Conversely, an increase in the same parameters of FITC was noticed in the double-labeled samples. The addition of pyrrole, an intercalator of DNA, enhanced both effects. These results suggest the existence of an electron interaction between TMR and FITC via long dsDNA coils of over 1000 bp.