Quantum dots are semiconductor nanoparticles with optical and electronic (optoelectronic) properties that vary with size and composition. They distinguish themselves from traditional fluorescence dyes due to their high visibility, long-lasting, size-tuneable, and narrow luminescence. Quantum dots are being used for a wide range of biological applications, including fluorescent assays for drug development, disease detection, single protein monitoring, and intracellular reporting. This mini review will focus on the overview of bioconjugation techniques which include the covalent and non-covalent conjugation of quantum dots surface to the active functional groups of carboxyl, amine, thiol, epoxy, hydroxyl and aldehyde. The various type of bioconjugation should be carefully selected based on the application of the quantum dots and the critical criteria of a biocompatible quantum dots will be also discussed. Recent application of quantum dots in biological system in bioimaging, bioanalytical, biosensing and drug delivery were laid out. The future outlook and the reality of quantum dots application in biological system were highlighted as the conclusion of this mini review.