We report the synthesis of CdSe/ZnSe/ZnS (core/shell/shell) quantum dots (QDs) as a fluorescence probe for biological cells, and their functionalization with carbon nanotube (CNT)-retrovirus complexes (labeled with the QDs) to form multi-functional tool with potential applications for cancer therapeutics. A mild method for preparing this QD-CNT-retrovirus complex, which preserves viral function, is reported. Observations and imaging under fluorescence confocal microscope show the expression of enhanced green fluorescent protein (EGFP) gene and QD uptake in viable cells, indicating that this novel probe is able to enter cells, crossing the natural barrier of the cell membranes. Such multi-functional probes have potential as medical diagnostics and for therapeutics for diseases including cancer. The multifunctional probe is of interest for potentially broad applications – with the quantum dots as the visualization aid, carbon nanotubes as an efficient opto-thermo converter for selective extermination of cells with the help of light irradiation at near-IR range, and the retrovirus as a vehicle for genetic therapy.